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| 1 | +/* | |
| 2 | + * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved. | |
| 3 | + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| 4 | + * | |
| 5 | + * This code is free software; you can redistribute it and/or modify it | |
| 6 | + * under the terms of the GNU General Public License version 2 only, as | |
| 7 | + * published by the Free Software Foundation. Oracle designates this | |
| 8 | + * particular file as subject to the "Classpath" exception as provided | |
| 9 | + * by Oracle in the LICENSE file that accompanied this code. | |
| 10 | + * | |
| 11 | + * This code is distributed in the hope that it will be useful, but WITHOUT | |
| 12 | + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 | + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 | + * version 2 for more details (a copy is included in the LICENSE file that | |
| 15 | + * accompanied this code). | |
| 16 | + * | |
| 17 | + * You should have received a copy of the GNU General Public License version | |
| 18 | + * 2 along with this work; if not, write to the Free Software Foundation, | |
| 19 | + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 20 | + * | |
| 21 | + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 22 | + * or visit www.oracle.com if you need additional information or have any | |
| 23 | + * questions. | |
| 24 | + */ | |
| 25 | + | |
| 26 | +package java.util; | |
| 27 | + | |
| 28 | +/** | |
| 29 | + * This class implements the Dual-Pivot Quicksort algorithm by | |
| 30 | + * Vladimir Yaroslavskiy, Jon Bentley, and Josh Bloch. The algorithm | |
| 31 | + * offers O(n log(n)) performance on many data sets that cause other | |
| 32 | + * quicksorts to degrade to quadratic performance, and is typically | |
| 33 | + * faster than traditional (one-pivot) Quicksort implementations. | |
| 34 | + * | |
| 35 | + * @author Vladimir Yaroslavskiy | |
| 36 | + * @author Jon Bentley | |
| 37 | + * @author Josh Bloch | |
| 38 | + * | |
| 39 | + * @version 2011.02.11 m765.827.12i:5\7pm | |
| 40 | + * @since 1.7 | |
| 41 | + */ | |
| 42 | +final class DualPivotQuicksort { | |
| 43 | + | |
| 44 | + /** | |
| 45 | + * Prevents instantiation. | |
| 46 | + */ | |
| 47 | + private DualPivotQuicksort() {} | |
| 48 | + | |
| 49 | + /* | |
| 50 | + * Tuning parameters. | |
| 51 | + */ | |
| 52 | + | |
| 53 | + /** | |
| 54 | + * The maximum number of runs in merge sort. | |
| 55 | + */ | |
| 56 | + private static final int MAX_RUN_COUNT = 67; | |
| 57 | + | |
| 58 | + /** | |
| 59 | + * The maximum length of run in merge sort. | |
| 60 | + */ | |
| 61 | + private static final int MAX_RUN_LENGTH = 33; | |
| 62 | + | |
| 63 | + /** | |
| 64 | + * If the length of an array to be sorted is less than this | |
| 65 | + * constant, Quicksort is used in preference to merge sort. | |
| 66 | + */ | |
| 67 | + private static final int QUICKSORT_THRESHOLD = 286; | |
| 68 | + | |
| 69 | + /** | |
| 70 | + * If the length of an array to be sorted is less than this | |
| 71 | + * constant, insertion sort is used in preference to Quicksort. | |
| 72 | + */ | |
| 73 | + private static final int INSERTION_SORT_THRESHOLD = 47; | |
| 74 | + | |
| 75 | + /** | |
| 76 | + * If the length of a byte array to be sorted is greater than this | |
| 77 | + * constant, counting sort is used in preference to insertion sort. | |
| 78 | + */ | |
| 79 | + private static final int COUNTING_SORT_THRESHOLD_FOR_BYTE = 29; | |
| 80 | + | |
| 81 | + /** | |
| 82 | + * If the length of a short or char array to be sorted is greater | |
| 83 | + * than this constant, counting sort is used in preference to Quicksort. | |
| 84 | + */ | |
| 85 | + private static final int COUNTING_SORT_THRESHOLD_FOR_SHORT_OR_CHAR = 3200; | |
| 86 | + | |
| 87 | + /* | |
| 88 | + * Sorting methods for seven primitive types. | |
| 89 | + */ | |
| 90 | + | |
| 91 | + /** | |
| 92 | + * Sorts the specified array. | |
| 93 | + * | |
| 94 | + * @param a the array to be sorted | |
| 95 | + */ | |
| 96 | + public static void sort(int[] a) { | |
| 97 | + sort(a, 0, a.length - 1); | |
| 98 | + } | |
| 99 | + | |
| 100 | + /** | |
| 101 | + * Sorts the specified range of the array. | |
| 102 | + * | |
| 103 | + * @param a the array to be sorted | |
| 104 | + * @param left the index of the first element, inclusive, to be sorted | |
| 105 | + * @param right the index of the last element, inclusive, to be sorted | |
| 106 | + */ | |
| 107 | + public static void sort(int[] a, int left, int right) { | |
| 108 | + // Use Quicksort on small arrays | |
| 109 | + if (right - left < QUICKSORT_THRESHOLD) { | |
| 110 | + sort(a, left, right, true); | |
| 111 | + return; | |
| 112 | + } | |
| 113 | + | |
| 114 | + /* | |
| 115 | + * Index run[i] is the start of i-th run | |
| 116 | + * (ascending or descending sequence). | |
| 117 | + */ | |
| 118 | + int[] run = new int[MAX_RUN_COUNT + 1]; | |
| 119 | + int count = 0; run[0] = left; | |
| 120 | + | |
| 121 | + // Check if the array is nearly sorted | |
| 122 | + for (int k = left; k < right; run[count] = k) { | |
| 123 | + if (a[k] < a[k + 1]) { // ascending | |
| 124 | + while (++k <= right && a[k - 1] <= a[k]); | |
| 125 | + } else if (a[k] > a[k + 1]) { // descending | |
| 126 | + while (++k <= right && a[k - 1] >= a[k]); | |
| 127 | + for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) { | |
| 128 | + int t = a[lo]; a[lo] = a[hi]; a[hi] = t; | |
| 129 | + } | |
| 130 | + } else { // equal | |
| 131 | + for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) { | |
| 132 | + if (--m == 0) { | |
| 133 | + sort(a, left, right, true); | |
| 134 | + return; | |
| 135 | + } | |
| 136 | + } | |
| 137 | + } | |
| 138 | + | |
| 139 | + /* | |
| 140 | + * The array is not highly structured, | |
| 141 | + * use Quicksort instead of merge sort. | |
| 142 | + */ | |
| 143 | + if (++count == MAX_RUN_COUNT) { | |
| 144 | + sort(a, left, right, true); | |
| 145 | + return; | |
| 146 | + } | |
| 147 | + } | |
| 148 | + | |
| 149 | + // Check special cases | |
| 150 | + if (run[count] == right++) { // The last run contains one element | |
| 151 | + run[++count] = right; | |
| 152 | + } else if (count == 1) { // The array is already sorted | |
| 153 | + return; | |
| 154 | + } | |
| 155 | + | |
| 156 | + /* | |
| 157 | + * Create temporary array, which is used for merging. | |
| 158 | + * Implementation note: variable "right" is increased by 1. | |
| 159 | + */ | |
| 160 | + int[] b; byte odd = 0; | |
| 161 | + for (int n = 1; (n <<= 1) < count; odd ^= 1); | |
| 162 | + | |
| 163 | + if (odd == 0) { | |
| 164 | + b = a; a = new int[b.length]; | |
| 165 | + for (int i = left - 1; ++i < right; a[i] = b[i]); | |
| 166 | + } else { | |
| 167 | + b = new int[a.length]; | |
| 168 | + } | |
| 169 | + | |
| 170 | + // Merging | |
| 171 | + for (int last; count > 1; count = last) { | |
| 172 | + for (int k = (last = 0) + 2; k <= count; k += 2) { | |
| 173 | + int hi = run[k], mi = run[k - 1]; | |
| 174 | + for (int i = run[k - 2], p = i, q = mi; i < hi; ++i) { | |
| 175 | + if (q >= hi || p < mi && a[p] <= a[q]) { | |
| 176 | + b[i] = a[p++]; | |
| 177 | + } else { | |
| 178 | + b[i] = a[q++]; | |
| 179 | + } | |
| 180 | + } | |
| 181 | + run[++last] = hi; | |
| 182 | + } | |
| 183 | + if ((count & 1) != 0) { | |
| 184 | + for (int i = right, lo = run[count - 1]; --i >= lo; | |
| 185 | + b[i] = a[i] | |
| 186 | + ); | |
| 187 | + run[++last] = right; | |
| 188 | + } | |
| 189 | + int[] t = a; a = b; b = t; | |
| 190 | + } | |
| 191 | + } | |
| 192 | + | |
| 193 | + /** | |
| 194 | + * Sorts the specified range of the array by Dual-Pivot Quicksort. | |
| 195 | + * | |
| 196 | + * @param a the array to be sorted | |
| 197 | + * @param left the index of the first element, inclusive, to be sorted | |
| 198 | + * @param right the index of the last element, inclusive, to be sorted | |
| 199 | + * @param leftmost indicates if this part is the leftmost in the range | |
| 200 | + */ | |
| 201 | + private static void sort(int[] a, int left, int right, boolean leftmost) { | |
| 202 | + int length = right - left + 1; | |
| 203 | + | |
| 204 | + // Use insertion sort on tiny arrays | |
| 205 | + if (length < INSERTION_SORT_THRESHOLD) { | |
| 206 | + if (leftmost) { | |
| 207 | + /* | |
| 208 | + * Traditional (without sentinel) insertion sort, | |
| 209 | + * optimized for server VM, is used in case of | |
| 210 | + * the leftmost part. | |
| 211 | + */ | |
| 212 | + for (int i = left, j = i; i < right; j = ++i) { | |
| 213 | + int ai = a[i + 1]; | |
| 214 | + while (ai < a[j]) { | |
| 215 | + a[j + 1] = a[j]; | |
| 216 | + if (j-- == left) { | |
| 217 | + break; | |
| 218 | + } | |
| 219 | + } | |
| 220 | + a[j + 1] = ai; | |
| 221 | + } | |
| 222 | + } else { | |
| 223 | + /* | |
| 224 | + * Skip the longest ascending sequence. | |
| 225 | + */ | |
| 226 | + do { | |
| 227 | + if (left >= right) { | |
| 228 | + return; | |
| 229 | + } | |
| 230 | + } while (a[++left] >= a[left - 1]); | |
| 231 | + | |
| 232 | + /* | |
| 233 | + * Every element from adjoining part plays the role | |
| 234 | + * of sentinel, therefore this allows us to avoid the | |
| 235 | + * left range check on each iteration. Moreover, we use | |
| 236 | + * the more optimized algorithm, so called pair insertion | |
| 237 | + * sort, which is faster (in the context of Quicksort) | |
| 238 | + * than traditional implementation of insertion sort. | |
| 239 | + */ | |
| 240 | + for (int k = left; ++left <= right; k = ++left) { | |
| 241 | + int a1 = a[k], a2 = a[left]; | |
| 242 | + | |
| 243 | + if (a1 < a2) { | |
| 244 | + a2 = a1; a1 = a[left]; | |
| 245 | + } | |
| 246 | + while (a1 < a[--k]) { | |
| 247 | + a[k + 2] = a[k]; | |
| 248 | + } | |
| 249 | + a[++k + 1] = a1; | |
| 250 | + | |
| 251 | + while (a2 < a[--k]) { | |
| 252 | + a[k + 1] = a[k]; | |
| 253 | + } | |
| 254 | + a[k + 1] = a2; | |
| 255 | + } | |
| 256 | + int last = a[right]; | |
| 257 | + | |
| 258 | + while (last < a[--right]) { | |
| 259 | + a[right + 1] = a[right]; | |
| 260 | + } | |
| 261 | + a[right + 1] = last; | |
| 262 | + } | |
| 263 | + return; | |
| 264 | + } | |
| 265 | + | |
| 266 | + // Inexpensive approximation of length / 7 | |
| 267 | + int seventh = (length >> 3) + (length >> 6) + 1; | |
| 268 | + | |
| 269 | + /* | |
| 270 | + * Sort five evenly spaced elements around (and including) the | |
| 271 | + * center element in the range. These elements will be used for | |
| 272 | + * pivot selection as described below. The choice for spacing | |
| 273 | + * these elements was empirically determined to work well on | |
| 274 | + * a wide variety of inputs. | |
| 275 | + */ | |
| 276 | + int e3 = (left + right) >>> 1; // The midpoint | |
| 277 | + int e2 = e3 - seventh; | |
| 278 | + int e1 = e2 - seventh; | |
| 279 | + int e4 = e3 + seventh; | |
| 280 | + int e5 = e4 + seventh; | |
| 281 | + | |
| 282 | + // Sort these elements using insertion sort | |
| 283 | + if (a[e2] < a[e1]) { int t = a[e2]; a[e2] = a[e1]; a[e1] = t; } | |
| 284 | + | |
| 285 | + if (a[e3] < a[e2]) { int t = a[e3]; a[e3] = a[e2]; a[e2] = t; | |
| 286 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 287 | + } | |
| 288 | + if (a[e4] < a[e3]) { int t = a[e4]; a[e4] = a[e3]; a[e3] = t; | |
| 289 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 290 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 291 | + } | |
| 292 | + } | |
| 293 | + if (a[e5] < a[e4]) { int t = a[e5]; a[e5] = a[e4]; a[e4] = t; | |
| 294 | + if (t < a[e3]) { a[e4] = a[e3]; a[e3] = t; | |
| 295 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 296 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 297 | + } | |
| 298 | + } | |
| 299 | + } | |
| 300 | + | |
| 301 | + // Pointers | |
| 302 | + int less = left; // The index of the first element of center part | |
| 303 | + int great = right; // The index before the first element of right part | |
| 304 | + | |
| 305 | + if (a[e1] != a[e2] && a[e2] != a[e3] && a[e3] != a[e4] && a[e4] != a[e5]) { | |
| 306 | + /* | |
| 307 | + * Use the second and fourth of the five sorted elements as pivots. | |
| 308 | + * These values are inexpensive approximations of the first and | |
| 309 | + * second terciles of the array. Note that pivot1 <= pivot2. | |
| 310 | + */ | |
| 311 | + int pivot1 = a[e2]; | |
| 312 | + int pivot2 = a[e4]; | |
| 313 | + | |
| 314 | + /* | |
| 315 | + * The first and the last elements to be sorted are moved to the | |
| 316 | + * locations formerly occupied by the pivots. When partitioning | |
| 317 | + * is complete, the pivots are swapped back into their final | |
| 318 | + * positions, and excluded from subsequent sorting. | |
| 319 | + */ | |
| 320 | + a[e2] = a[left]; | |
| 321 | + a[e4] = a[right]; | |
| 322 | + | |
| 323 | + /* | |
| 324 | + * Skip elements, which are less or greater than pivot values. | |
| 325 | + */ | |
| 326 | + while (a[++less] < pivot1); | |
| 327 | + while (a[--great] > pivot2); | |
| 328 | + | |
| 329 | + /* | |
| 330 | + * Partitioning: | |
| 331 | + * | |
| 332 | + * left part center part right part | |
| 333 | + * +--------------------------------------------------------------+ | |
| 334 | + * | < pivot1 | pivot1 <= && <= pivot2 | ? | > pivot2 | | |
| 335 | + * +--------------------------------------------------------------+ | |
| 336 | + * ^ ^ ^ | |
| 337 | + * | | | | |
| 338 | + * less k great | |
| 339 | + * | |
| 340 | + * Invariants: | |
| 341 | + * | |
| 342 | + * all in (left, less) < pivot1 | |
| 343 | + * pivot1 <= all in [less, k) <= pivot2 | |
| 344 | + * all in (great, right) > pivot2 | |
| 345 | + * | |
| 346 | + * Pointer k is the first index of ?-part. | |
| 347 | + */ | |
| 348 | + outer: | |
| 349 | + for (int k = less - 1; ++k <= great; ) { | |
| 350 | + int ak = a[k]; | |
| 351 | + if (ak < pivot1) { // Move a[k] to left part | |
| 352 | + a[k] = a[less]; | |
| 353 | + /* | |
| 354 | + * Here and below we use "a[i] = b; i++;" instead | |
| 355 | + * of "a[i++] = b;" due to performance issue. | |
| 356 | + */ | |
| 357 | + a[less] = ak; | |
| 358 | + ++less; | |
| 359 | + } else if (ak > pivot2) { // Move a[k] to right part | |
| 360 | + while (a[great] > pivot2) { | |
| 361 | + if (great-- == k) { | |
| 362 | + break outer; | |
| 363 | + } | |
| 364 | + } | |
| 365 | + if (a[great] < pivot1) { // a[great] <= pivot2 | |
| 366 | + a[k] = a[less]; | |
| 367 | + a[less] = a[great]; | |
| 368 | + ++less; | |
| 369 | + } else { // pivot1 <= a[great] <= pivot2 | |
| 370 | + a[k] = a[great]; | |
| 371 | + } | |
| 372 | + /* | |
| 373 | + * Here and below we use "a[i] = b; i--;" instead | |
| 374 | + * of "a[i--] = b;" due to performance issue. | |
| 375 | + */ | |
| 376 | + a[great] = ak; | |
| 377 | + --great; | |
| 378 | + } | |
| 379 | + } | |
| 380 | + | |
| 381 | + // Swap pivots into their final positions | |
| 382 | + a[left] = a[less - 1]; a[less - 1] = pivot1; | |
| 383 | + a[right] = a[great + 1]; a[great + 1] = pivot2; | |
| 384 | + | |
| 385 | + // Sort left and right parts recursively, excluding known pivots | |
| 386 | + sort(a, left, less - 2, leftmost); | |
| 387 | + sort(a, great + 2, right, false); | |
| 388 | + | |
| 389 | + /* | |
| 390 | + * If center part is too large (comprises > 4/7 of the array), | |
| 391 | + * swap internal pivot values to ends. | |
| 392 | + */ | |
| 393 | + if (less < e1 && e5 < great) { | |
| 394 | + /* | |
| 395 | + * Skip elements, which are equal to pivot values. | |
| 396 | + */ | |
| 397 | + while (a[less] == pivot1) { | |
| 398 | + ++less; | |
| 399 | + } | |
| 400 | + | |
| 401 | + while (a[great] == pivot2) { | |
| 402 | + --great; | |
| 403 | + } | |
| 404 | + | |
| 405 | + /* | |
| 406 | + * Partitioning: | |
| 407 | + * | |
| 408 | + * left part center part right part | |
| 409 | + * +----------------------------------------------------------+ | |
| 410 | + * | == pivot1 | pivot1 < && < pivot2 | ? | == pivot2 | | |
| 411 | + * +----------------------------------------------------------+ | |
| 412 | + * ^ ^ ^ | |
| 413 | + * | | | | |
| 414 | + * less k great | |
| 415 | + * | |
| 416 | + * Invariants: | |
| 417 | + * | |
| 418 | + * all in (*, less) == pivot1 | |
| 419 | + * pivot1 < all in [less, k) < pivot2 | |
| 420 | + * all in (great, *) == pivot2 | |
| 421 | + * | |
| 422 | + * Pointer k is the first index of ?-part. | |
| 423 | + */ | |
| 424 | + outer: | |
| 425 | + for (int k = less - 1; ++k <= great; ) { | |
| 426 | + int ak = a[k]; | |
| 427 | + if (ak == pivot1) { // Move a[k] to left part | |
| 428 | + a[k] = a[less]; | |
| 429 | + a[less] = ak; | |
| 430 | + ++less; | |
| 431 | + } else if (ak == pivot2) { // Move a[k] to right part | |
| 432 | + while (a[great] == pivot2) { | |
| 433 | + if (great-- == k) { | |
| 434 | + break outer; | |
| 435 | + } | |
| 436 | + } | |
| 437 | + if (a[great] == pivot1) { // a[great] < pivot2 | |
| 438 | + a[k] = a[less]; | |
| 439 | + /* | |
| 440 | + * Even though a[great] equals to pivot1, the | |
| 441 | + * assignment a[less] = pivot1 may be incorrect, | |
| 442 | + * if a[great] and pivot1 are floating-point zeros | |
| 443 | + * of different signs. Therefore in float and | |
| 444 | + * double sorting methods we have to use more | |
| 445 | + * accurate assignment a[less] = a[great]. | |
| 446 | + */ | |
| 447 | + a[less] = pivot1; | |
| 448 | + ++less; | |
| 449 | + } else { // pivot1 < a[great] < pivot2 | |
| 450 | + a[k] = a[great]; | |
| 451 | + } | |
| 452 | + a[great] = ak; | |
| 453 | + --great; | |
| 454 | + } | |
| 455 | + } | |
| 456 | + } | |
| 457 | + | |
| 458 | + // Sort center part recursively | |
| 459 | + sort(a, less, great, false); | |
| 460 | + | |
| 461 | + } else { // Partitioning with one pivot | |
| 462 | + /* | |
| 463 | + * Use the third of the five sorted elements as pivot. | |
| 464 | + * This value is inexpensive approximation of the median. | |
| 465 | + */ | |
| 466 | + int pivot = a[e3]; | |
| 467 | + | |
| 468 | + /* | |
| 469 | + * Partitioning degenerates to the traditional 3-way | |
| 470 | + * (or "Dutch National Flag") schema: | |
| 471 | + * | |
| 472 | + * left part center part right part | |
| 473 | + * +-------------------------------------------------+ | |
| 474 | + * | < pivot | == pivot | ? | > pivot | | |
| 475 | + * +-------------------------------------------------+ | |
| 476 | + * ^ ^ ^ | |
| 477 | + * | | | | |
| 478 | + * less k great | |
| 479 | + * | |
| 480 | + * Invariants: | |
| 481 | + * | |
| 482 | + * all in (left, less) < pivot | |
| 483 | + * all in [less, k) == pivot | |
| 484 | + * all in (great, right) > pivot | |
| 485 | + * | |
| 486 | + * Pointer k is the first index of ?-part. | |
| 487 | + */ | |
| 488 | + for (int k = less; k <= great; ++k) { | |
| 489 | + if (a[k] == pivot) { | |
| 490 | + continue; | |
| 491 | + } | |
| 492 | + int ak = a[k]; | |
| 493 | + if (ak < pivot) { // Move a[k] to left part | |
| 494 | + a[k] = a[less]; | |
| 495 | + a[less] = ak; | |
| 496 | + ++less; | |
| 497 | + } else { // a[k] > pivot - Move a[k] to right part | |
| 498 | + while (a[great] > pivot) { | |
| 499 | + --great; | |
| 500 | + } | |
| 501 | + if (a[great] < pivot) { // a[great] <= pivot | |
| 502 | + a[k] = a[less]; | |
| 503 | + a[less] = a[great]; | |
| 504 | + ++less; | |
| 505 | + } else { // a[great] == pivot | |
| 506 | + /* | |
| 507 | + * Even though a[great] equals to pivot, the | |
| 508 | + * assignment a[k] = pivot may be incorrect, | |
| 509 | + * if a[great] and pivot are floating-point | |
| 510 | + * zeros of different signs. Therefore in float | |
| 511 | + * and double sorting methods we have to use | |
| 512 | + * more accurate assignment a[k] = a[great]. | |
| 513 | + */ | |
| 514 | + a[k] = pivot; | |
| 515 | + } | |
| 516 | + a[great] = ak; | |
| 517 | + --great; | |
| 518 | + } | |
| 519 | + } | |
| 520 | + | |
| 521 | + /* | |
| 522 | + * Sort left and right parts recursively. | |
| 523 | + * All elements from center part are equal | |
| 524 | + * and, therefore, already sorted. | |
| 525 | + */ | |
| 526 | + sort(a, left, less - 1, leftmost); | |
| 527 | + sort(a, great + 1, right, false); | |
| 528 | + } | |
| 529 | + } | |
| 530 | + | |
| 531 | + /** | |
| 532 | + * Sorts the specified array. | |
| 533 | + * | |
| 534 | + * @param a the array to be sorted | |
| 535 | + */ | |
| 536 | + public static void sort(long[] a) { | |
| 537 | + sort(a, 0, a.length - 1); | |
| 538 | + } | |
| 539 | + | |
| 540 | + /** | |
| 541 | + * Sorts the specified range of the array. | |
| 542 | + * | |
| 543 | + * @param a the array to be sorted | |
| 544 | + * @param left the index of the first element, inclusive, to be sorted | |
| 545 | + * @param right the index of the last element, inclusive, to be sorted | |
| 546 | + */ | |
| 547 | + public static void sort(long[] a, int left, int right) { | |
| 548 | + // Use Quicksort on small arrays | |
| 549 | + if (right - left < QUICKSORT_THRESHOLD) { | |
| 550 | + sort(a, left, right, true); | |
| 551 | + return; | |
| 552 | + } | |
| 553 | + | |
| 554 | + /* | |
| 555 | + * Index run[i] is the start of i-th run | |
| 556 | + * (ascending or descending sequence). | |
| 557 | + */ | |
| 558 | + int[] run = new int[MAX_RUN_COUNT + 1]; | |
| 559 | + int count = 0; run[0] = left; | |
| 560 | + | |
| 561 | + // Check if the array is nearly sorted | |
| 562 | + for (int k = left; k < right; run[count] = k) { | |
| 563 | + if (a[k] < a[k + 1]) { // ascending | |
| 564 | + while (++k <= right && a[k - 1] <= a[k]); | |
| 565 | + } else if (a[k] > a[k + 1]) { // descending | |
| 566 | + while (++k <= right && a[k - 1] >= a[k]); | |
| 567 | + for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) { | |
| 568 | + long t = a[lo]; a[lo] = a[hi]; a[hi] = t; | |
| 569 | + } | |
| 570 | + } else { // equal | |
| 571 | + for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) { | |
| 572 | + if (--m == 0) { | |
| 573 | + sort(a, left, right, true); | |
| 574 | + return; | |
| 575 | + } | |
| 576 | + } | |
| 577 | + } | |
| 578 | + | |
| 579 | + /* | |
| 580 | + * The array is not highly structured, | |
| 581 | + * use Quicksort instead of merge sort. | |
| 582 | + */ | |
| 583 | + if (++count == MAX_RUN_COUNT) { | |
| 584 | + sort(a, left, right, true); | |
| 585 | + return; | |
| 586 | + } | |
| 587 | + } | |
| 588 | + | |
| 589 | + // Check special cases | |
| 590 | + if (run[count] == right++) { // The last run contains one element | |
| 591 | + run[++count] = right; | |
| 592 | + } else if (count == 1) { // The array is already sorted | |
| 593 | + return; | |
| 594 | + } | |
| 595 | + | |
| 596 | + /* | |
| 597 | + * Create temporary array, which is used for merging. | |
| 598 | + * Implementation note: variable "right" is increased by 1. | |
| 599 | + */ | |
| 600 | + long[] b; byte odd = 0; | |
| 601 | + for (int n = 1; (n <<= 1) < count; odd ^= 1); | |
| 602 | + | |
| 603 | + if (odd == 0) { | |
| 604 | + b = a; a = new long[b.length]; | |
| 605 | + for (int i = left - 1; ++i < right; a[i] = b[i]); | |
| 606 | + } else { | |
| 607 | + b = new long[a.length]; | |
| 608 | + } | |
| 609 | + | |
| 610 | + // Merging | |
| 611 | + for (int last; count > 1; count = last) { | |
| 612 | + for (int k = (last = 0) + 2; k <= count; k += 2) { | |
| 613 | + int hi = run[k], mi = run[k - 1]; | |
| 614 | + for (int i = run[k - 2], p = i, q = mi; i < hi; ++i) { | |
| 615 | + if (q >= hi || p < mi && a[p] <= a[q]) { | |
| 616 | + b[i] = a[p++]; | |
| 617 | + } else { | |
| 618 | + b[i] = a[q++]; | |
| 619 | + } | |
| 620 | + } | |
| 621 | + run[++last] = hi; | |
| 622 | + } | |
| 623 | + if ((count & 1) != 0) { | |
| 624 | + for (int i = right, lo = run[count - 1]; --i >= lo; | |
| 625 | + b[i] = a[i] | |
| 626 | + ); | |
| 627 | + run[++last] = right; | |
| 628 | + } | |
| 629 | + long[] t = a; a = b; b = t; | |
| 630 | + } | |
| 631 | + } | |
| 632 | + | |
| 633 | + /** | |
| 634 | + * Sorts the specified range of the array by Dual-Pivot Quicksort. | |
| 635 | + * | |
| 636 | + * @param a the array to be sorted | |
| 637 | + * @param left the index of the first element, inclusive, to be sorted | |
| 638 | + * @param right the index of the last element, inclusive, to be sorted | |
| 639 | + * @param leftmost indicates if this part is the leftmost in the range | |
| 640 | + */ | |
| 641 | + private static void sort(long[] a, int left, int right, boolean leftmost) { | |
| 642 | + int length = right - left + 1; | |
| 643 | + | |
| 644 | + // Use insertion sort on tiny arrays | |
| 645 | + if (length < INSERTION_SORT_THRESHOLD) { | |
| 646 | + if (leftmost) { | |
| 647 | + /* | |
| 648 | + * Traditional (without sentinel) insertion sort, | |
| 649 | + * optimized for server VM, is used in case of | |
| 650 | + * the leftmost part. | |
| 651 | + */ | |
| 652 | + for (int i = left, j = i; i < right; j = ++i) { | |
| 653 | + long ai = a[i + 1]; | |
| 654 | + while (ai < a[j]) { | |
| 655 | + a[j + 1] = a[j]; | |
| 656 | + if (j-- == left) { | |
| 657 | + break; | |
| 658 | + } | |
| 659 | + } | |
| 660 | + a[j + 1] = ai; | |
| 661 | + } | |
| 662 | + } else { | |
| 663 | + /* | |
| 664 | + * Skip the longest ascending sequence. | |
| 665 | + */ | |
| 666 | + do { | |
| 667 | + if (left >= right) { | |
| 668 | + return; | |
| 669 | + } | |
| 670 | + } while (a[++left] >= a[left - 1]); | |
| 671 | + | |
| 672 | + /* | |
| 673 | + * Every element from adjoining part plays the role | |
| 674 | + * of sentinel, therefore this allows us to avoid the | |
| 675 | + * left range check on each iteration. Moreover, we use | |
| 676 | + * the more optimized algorithm, so called pair insertion | |
| 677 | + * sort, which is faster (in the context of Quicksort) | |
| 678 | + * than traditional implementation of insertion sort. | |
| 679 | + */ | |
| 680 | + for (int k = left; ++left <= right; k = ++left) { | |
| 681 | + long a1 = a[k], a2 = a[left]; | |
| 682 | + | |
| 683 | + if (a1 < a2) { | |
| 684 | + a2 = a1; a1 = a[left]; | |
| 685 | + } | |
| 686 | + while (a1 < a[--k]) { | |
| 687 | + a[k + 2] = a[k]; | |
| 688 | + } | |
| 689 | + a[++k + 1] = a1; | |
| 690 | + | |
| 691 | + while (a2 < a[--k]) { | |
| 692 | + a[k + 1] = a[k]; | |
| 693 | + } | |
| 694 | + a[k + 1] = a2; | |
| 695 | + } | |
| 696 | + long last = a[right]; | |
| 697 | + | |
| 698 | + while (last < a[--right]) { | |
| 699 | + a[right + 1] = a[right]; | |
| 700 | + } | |
| 701 | + a[right + 1] = last; | |
| 702 | + } | |
| 703 | + return; | |
| 704 | + } | |
| 705 | + | |
| 706 | + // Inexpensive approximation of length / 7 | |
| 707 | + int seventh = (length >> 3) + (length >> 6) + 1; | |
| 708 | + | |
| 709 | + /* | |
| 710 | + * Sort five evenly spaced elements around (and including) the | |
| 711 | + * center element in the range. These elements will be used for | |
| 712 | + * pivot selection as described below. The choice for spacing | |
| 713 | + * these elements was empirically determined to work well on | |
| 714 | + * a wide variety of inputs. | |
| 715 | + */ | |
| 716 | + int e3 = (left + right) >>> 1; // The midpoint | |
| 717 | + int e2 = e3 - seventh; | |
| 718 | + int e1 = e2 - seventh; | |
| 719 | + int e4 = e3 + seventh; | |
| 720 | + int e5 = e4 + seventh; | |
| 721 | + | |
| 722 | + // Sort these elements using insertion sort | |
| 723 | + if (a[e2] < a[e1]) { long t = a[e2]; a[e2] = a[e1]; a[e1] = t; } | |
| 724 | + | |
| 725 | + if (a[e3] < a[e2]) { long t = a[e3]; a[e3] = a[e2]; a[e2] = t; | |
| 726 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 727 | + } | |
| 728 | + if (a[e4] < a[e3]) { long t = a[e4]; a[e4] = a[e3]; a[e3] = t; | |
| 729 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 730 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 731 | + } | |
| 732 | + } | |
| 733 | + if (a[e5] < a[e4]) { long t = a[e5]; a[e5] = a[e4]; a[e4] = t; | |
| 734 | + if (t < a[e3]) { a[e4] = a[e3]; a[e3] = t; | |
| 735 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 736 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 737 | + } | |
| 738 | + } | |
| 739 | + } | |
| 740 | + | |
| 741 | + // Pointers | |
| 742 | + int less = left; // The index of the first element of center part | |
| 743 | + int great = right; // The index before the first element of right part | |
| 744 | + | |
| 745 | + if (a[e1] != a[e2] && a[e2] != a[e3] && a[e3] != a[e4] && a[e4] != a[e5]) { | |
| 746 | + /* | |
| 747 | + * Use the second and fourth of the five sorted elements as pivots. | |
| 748 | + * These values are inexpensive approximations of the first and | |
| 749 | + * second terciles of the array. Note that pivot1 <= pivot2. | |
| 750 | + */ | |
| 751 | + long pivot1 = a[e2]; | |
| 752 | + long pivot2 = a[e4]; | |
| 753 | + | |
| 754 | + /* | |
| 755 | + * The first and the last elements to be sorted are moved to the | |
| 756 | + * locations formerly occupied by the pivots. When partitioning | |
| 757 | + * is complete, the pivots are swapped back into their final | |
| 758 | + * positions, and excluded from subsequent sorting. | |
| 759 | + */ | |
| 760 | + a[e2] = a[left]; | |
| 761 | + a[e4] = a[right]; | |
| 762 | + | |
| 763 | + /* | |
| 764 | + * Skip elements, which are less or greater than pivot values. | |
| 765 | + */ | |
| 766 | + while (a[++less] < pivot1); | |
| 767 | + while (a[--great] > pivot2); | |
| 768 | + | |
| 769 | + /* | |
| 770 | + * Partitioning: | |
| 771 | + * | |
| 772 | + * left part center part right part | |
| 773 | + * +--------------------------------------------------------------+ | |
| 774 | + * | < pivot1 | pivot1 <= && <= pivot2 | ? | > pivot2 | | |
| 775 | + * +--------------------------------------------------------------+ | |
| 776 | + * ^ ^ ^ | |
| 777 | + * | | | | |
| 778 | + * less k great | |
| 779 | + * | |
| 780 | + * Invariants: | |
| 781 | + * | |
| 782 | + * all in (left, less) < pivot1 | |
| 783 | + * pivot1 <= all in [less, k) <= pivot2 | |
| 784 | + * all in (great, right) > pivot2 | |
| 785 | + * | |
| 786 | + * Pointer k is the first index of ?-part. | |
| 787 | + */ | |
| 788 | + outer: | |
| 789 | + for (int k = less - 1; ++k <= great; ) { | |
| 790 | + long ak = a[k]; | |
| 791 | + if (ak < pivot1) { // Move a[k] to left part | |
| 792 | + a[k] = a[less]; | |
| 793 | + /* | |
| 794 | + * Here and below we use "a[i] = b; i++;" instead | |
| 795 | + * of "a[i++] = b;" due to performance issue. | |
| 796 | + */ | |
| 797 | + a[less] = ak; | |
| 798 | + ++less; | |
| 799 | + } else if (ak > pivot2) { // Move a[k] to right part | |
| 800 | + while (a[great] > pivot2) { | |
| 801 | + if (great-- == k) { | |
| 802 | + break outer; | |
| 803 | + } | |
| 804 | + } | |
| 805 | + if (a[great] < pivot1) { // a[great] <= pivot2 | |
| 806 | + a[k] = a[less]; | |
| 807 | + a[less] = a[great]; | |
| 808 | + ++less; | |
| 809 | + } else { // pivot1 <= a[great] <= pivot2 | |
| 810 | + a[k] = a[great]; | |
| 811 | + } | |
| 812 | + /* | |
| 813 | + * Here and below we use "a[i] = b; i--;" instead | |
| 814 | + * of "a[i--] = b;" due to performance issue. | |
| 815 | + */ | |
| 816 | + a[great] = ak; | |
| 817 | + --great; | |
| 818 | + } | |
| 819 | + } | |
| 820 | + | |
| 821 | + // Swap pivots into their final positions | |
| 822 | + a[left] = a[less - 1]; a[less - 1] = pivot1; | |
| 823 | + a[right] = a[great + 1]; a[great + 1] = pivot2; | |
| 824 | + | |
| 825 | + // Sort left and right parts recursively, excluding known pivots | |
| 826 | + sort(a, left, less - 2, leftmost); | |
| 827 | + sort(a, great + 2, right, false); | |
| 828 | + | |
| 829 | + /* | |
| 830 | + * If center part is too large (comprises > 4/7 of the array), | |
| 831 | + * swap internal pivot values to ends. | |
| 832 | + */ | |
| 833 | + if (less < e1 && e5 < great) { | |
| 834 | + /* | |
| 835 | + * Skip elements, which are equal to pivot values. | |
| 836 | + */ | |
| 837 | + while (a[less] == pivot1) { | |
| 838 | + ++less; | |
| 839 | + } | |
| 840 | + | |
| 841 | + while (a[great] == pivot2) { | |
| 842 | + --great; | |
| 843 | + } | |
| 844 | + | |
| 845 | + /* | |
| 846 | + * Partitioning: | |
| 847 | + * | |
| 848 | + * left part center part right part | |
| 849 | + * +----------------------------------------------------------+ | |
| 850 | + * | == pivot1 | pivot1 < && < pivot2 | ? | == pivot2 | | |
| 851 | + * +----------------------------------------------------------+ | |
| 852 | + * ^ ^ ^ | |
| 853 | + * | | | | |
| 854 | + * less k great | |
| 855 | + * | |
| 856 | + * Invariants: | |
| 857 | + * | |
| 858 | + * all in (*, less) == pivot1 | |
| 859 | + * pivot1 < all in [less, k) < pivot2 | |
| 860 | + * all in (great, *) == pivot2 | |
| 861 | + * | |
| 862 | + * Pointer k is the first index of ?-part. | |
| 863 | + */ | |
| 864 | + outer: | |
| 865 | + for (int k = less - 1; ++k <= great; ) { | |
| 866 | + long ak = a[k]; | |
| 867 | + if (ak == pivot1) { // Move a[k] to left part | |
| 868 | + a[k] = a[less]; | |
| 869 | + a[less] = ak; | |
| 870 | + ++less; | |
| 871 | + } else if (ak == pivot2) { // Move a[k] to right part | |
| 872 | + while (a[great] == pivot2) { | |
| 873 | + if (great-- == k) { | |
| 874 | + break outer; | |
| 875 | + } | |
| 876 | + } | |
| 877 | + if (a[great] == pivot1) { // a[great] < pivot2 | |
| 878 | + a[k] = a[less]; | |
| 879 | + /* | |
| 880 | + * Even though a[great] equals to pivot1, the | |
| 881 | + * assignment a[less] = pivot1 may be incorrect, | |
| 882 | + * if a[great] and pivot1 are floating-point zeros | |
| 883 | + * of different signs. Therefore in float and | |
| 884 | + * double sorting methods we have to use more | |
| 885 | + * accurate assignment a[less] = a[great]. | |
| 886 | + */ | |
| 887 | + a[less] = pivot1; | |
| 888 | + ++less; | |
| 889 | + } else { // pivot1 < a[great] < pivot2 | |
| 890 | + a[k] = a[great]; | |
| 891 | + } | |
| 892 | + a[great] = ak; | |
| 893 | + --great; | |
| 894 | + } | |
| 895 | + } | |
| 896 | + } | |
| 897 | + | |
| 898 | + // Sort center part recursively | |
| 899 | + sort(a, less, great, false); | |
| 900 | + | |
| 901 | + } else { // Partitioning with one pivot | |
| 902 | + /* | |
| 903 | + * Use the third of the five sorted elements as pivot. | |
| 904 | + * This value is inexpensive approximation of the median. | |
| 905 | + */ | |
| 906 | + long pivot = a[e3]; | |
| 907 | + | |
| 908 | + /* | |
| 909 | + * Partitioning degenerates to the traditional 3-way | |
| 910 | + * (or "Dutch National Flag") schema: | |
| 911 | + * | |
| 912 | + * left part center part right part | |
| 913 | + * +-------------------------------------------------+ | |
| 914 | + * | < pivot | == pivot | ? | > pivot | | |
| 915 | + * +-------------------------------------------------+ | |
| 916 | + * ^ ^ ^ | |
| 917 | + * | | | | |
| 918 | + * less k great | |
| 919 | + * | |
| 920 | + * Invariants: | |
| 921 | + * | |
| 922 | + * all in (left, less) < pivot | |
| 923 | + * all in [less, k) == pivot | |
| 924 | + * all in (great, right) > pivot | |
| 925 | + * | |
| 926 | + * Pointer k is the first index of ?-part. | |
| 927 | + */ | |
| 928 | + for (int k = less; k <= great; ++k) { | |
| 929 | + if (a[k] == pivot) { | |
| 930 | + continue; | |
| 931 | + } | |
| 932 | + long ak = a[k]; | |
| 933 | + if (ak < pivot) { // Move a[k] to left part | |
| 934 | + a[k] = a[less]; | |
| 935 | + a[less] = ak; | |
| 936 | + ++less; | |
| 937 | + } else { // a[k] > pivot - Move a[k] to right part | |
| 938 | + while (a[great] > pivot) { | |
| 939 | + --great; | |
| 940 | + } | |
| 941 | + if (a[great] < pivot) { // a[great] <= pivot | |
| 942 | + a[k] = a[less]; | |
| 943 | + a[less] = a[great]; | |
| 944 | + ++less; | |
| 945 | + } else { // a[great] == pivot | |
| 946 | + /* | |
| 947 | + * Even though a[great] equals to pivot, the | |
| 948 | + * assignment a[k] = pivot may be incorrect, | |
| 949 | + * if a[great] and pivot are floating-point | |
| 950 | + * zeros of different signs. Therefore in float | |
| 951 | + * and double sorting methods we have to use | |
| 952 | + * more accurate assignment a[k] = a[great]. | |
| 953 | + */ | |
| 954 | + a[k] = pivot; | |
| 955 | + } | |
| 956 | + a[great] = ak; | |
| 957 | + --great; | |
| 958 | + } | |
| 959 | + } | |
| 960 | + | |
| 961 | + /* | |
| 962 | + * Sort left and right parts recursively. | |
| 963 | + * All elements from center part are equal | |
| 964 | + * and, therefore, already sorted. | |
| 965 | + */ | |
| 966 | + sort(a, left, less - 1, leftmost); | |
| 967 | + sort(a, great + 1, right, false); | |
| 968 | + } | |
| 969 | + } | |
| 970 | + | |
| 971 | + /** | |
| 972 | + * Sorts the specified array. | |
| 973 | + * | |
| 974 | + * @param a the array to be sorted | |
| 975 | + */ | |
| 976 | + public static void sort(short[] a) { | |
| 977 | + sort(a, 0, a.length - 1); | |
| 978 | + } | |
| 979 | + | |
| 980 | + /** | |
| 981 | + * Sorts the specified range of the array. | |
| 982 | + * | |
| 983 | + * @param a the array to be sorted | |
| 984 | + * @param left the index of the first element, inclusive, to be sorted | |
| 985 | + * @param right the index of the last element, inclusive, to be sorted | |
| 986 | + */ | |
| 987 | + public static void sort(short[] a, int left, int right) { | |
| 988 | + // Use counting sort on large arrays | |
| 989 | + if (right - left > COUNTING_SORT_THRESHOLD_FOR_SHORT_OR_CHAR) { | |
| 990 | + int[] count = new int[NUM_SHORT_VALUES]; | |
| 991 | + | |
| 992 | + for (int i = left - 1; ++i <= right; | |
| 993 | + count[a[i] - Short.MIN_VALUE]++ | |
| 994 | + ); | |
| 995 | + for (int i = NUM_SHORT_VALUES, k = right + 1; k > left; ) { | |
| 996 | + while (count[--i] == 0); | |
| 997 | + short value = (short) (i + Short.MIN_VALUE); | |
| 998 | + int s = count[i]; | |
| 999 | + | |
| 1000 | + do { | |
| 1001 | + a[--k] = value; | |
| 1002 | + } while (--s > 0); | |
| 1003 | + } | |
| 1004 | + } else { // Use Dual-Pivot Quicksort on small arrays | |
| 1005 | + doSort(a, left, right); | |
| 1006 | + } | |
| 1007 | + } | |
| 1008 | + | |
| 1009 | + /** The number of distinct short values. */ | |
| 1010 | + private static final int NUM_SHORT_VALUES = 1 << 16; | |
| 1011 | + | |
| 1012 | + /** | |
| 1013 | + * Sorts the specified range of the array. | |
| 1014 | + * | |
| 1015 | + * @param a the array to be sorted | |
| 1016 | + * @param left the index of the first element, inclusive, to be sorted | |
| 1017 | + * @param right the index of the last element, inclusive, to be sorted | |
| 1018 | + */ | |
| 1019 | + private static void doSort(short[] a, int left, int right) { | |
| 1020 | + // Use Quicksort on small arrays | |
| 1021 | + if (right - left < QUICKSORT_THRESHOLD) { | |
| 1022 | + sort(a, left, right, true); | |
| 1023 | + return; | |
| 1024 | + } | |
| 1025 | + | |
| 1026 | + /* | |
| 1027 | + * Index run[i] is the start of i-th run | |
| 1028 | + * (ascending or descending sequence). | |
| 1029 | + */ | |
| 1030 | + int[] run = new int[MAX_RUN_COUNT + 1]; | |
| 1031 | + int count = 0; run[0] = left; | |
| 1032 | + | |
| 1033 | + // Check if the array is nearly sorted | |
| 1034 | + for (int k = left; k < right; run[count] = k) { | |
| 1035 | + if (a[k] < a[k + 1]) { // ascending | |
| 1036 | + while (++k <= right && a[k - 1] <= a[k]); | |
| 1037 | + } else if (a[k] > a[k + 1]) { // descending | |
| 1038 | + while (++k <= right && a[k - 1] >= a[k]); | |
| 1039 | + for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) { | |
| 1040 | + short t = a[lo]; a[lo] = a[hi]; a[hi] = t; | |
| 1041 | + } | |
| 1042 | + } else { // equal | |
| 1043 | + for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) { | |
| 1044 | + if (--m == 0) { | |
| 1045 | + sort(a, left, right, true); | |
| 1046 | + return; | |
| 1047 | + } | |
| 1048 | + } | |
| 1049 | + } | |
| 1050 | + | |
| 1051 | + /* | |
| 1052 | + * The array is not highly structured, | |
| 1053 | + * use Quicksort instead of merge sort. | |
| 1054 | + */ | |
| 1055 | + if (++count == MAX_RUN_COUNT) { | |
| 1056 | + sort(a, left, right, true); | |
| 1057 | + return; | |
| 1058 | + } | |
| 1059 | + } | |
| 1060 | + | |
| 1061 | + // Check special cases | |
| 1062 | + if (run[count] == right++) { // The last run contains one element | |
| 1063 | + run[++count] = right; | |
| 1064 | + } else if (count == 1) { // The array is already sorted | |
| 1065 | + return; | |
| 1066 | + } | |
| 1067 | + | |
| 1068 | + /* | |
| 1069 | + * Create temporary array, which is used for merging. | |
| 1070 | + * Implementation note: variable "right" is increased by 1. | |
| 1071 | + */ | |
| 1072 | + short[] b; byte odd = 0; | |
| 1073 | + for (int n = 1; (n <<= 1) < count; odd ^= 1); | |
| 1074 | + | |
| 1075 | + if (odd == 0) { | |
| 1076 | + b = a; a = new short[b.length]; | |
| 1077 | + for (int i = left - 1; ++i < right; a[i] = b[i]); | |
| 1078 | + } else { | |
| 1079 | + b = new short[a.length]; | |
| 1080 | + } | |
| 1081 | + | |
| 1082 | + // Merging | |
| 1083 | + for (int last; count > 1; count = last) { | |
| 1084 | + for (int k = (last = 0) + 2; k <= count; k += 2) { | |
| 1085 | + int hi = run[k], mi = run[k - 1]; | |
| 1086 | + for (int i = run[k - 2], p = i, q = mi; i < hi; ++i) { | |
| 1087 | + if (q >= hi || p < mi && a[p] <= a[q]) { | |
| 1088 | + b[i] = a[p++]; | |
| 1089 | + } else { | |
| 1090 | + b[i] = a[q++]; | |
| 1091 | + } | |
| 1092 | + } | |
| 1093 | + run[++last] = hi; | |
| 1094 | + } | |
| 1095 | + if ((count & 1) != 0) { | |
| 1096 | + for (int i = right, lo = run[count - 1]; --i >= lo; | |
| 1097 | + b[i] = a[i] | |
| 1098 | + ); | |
| 1099 | + run[++last] = right; | |
| 1100 | + } | |
| 1101 | + short[] t = a; a = b; b = t; | |
| 1102 | + } | |
| 1103 | + } | |
| 1104 | + | |
| 1105 | + /** | |
| 1106 | + * Sorts the specified range of the array by Dual-Pivot Quicksort. | |
| 1107 | + * | |
| 1108 | + * @param a the array to be sorted | |
| 1109 | + * @param left the index of the first element, inclusive, to be sorted | |
| 1110 | + * @param right the index of the last element, inclusive, to be sorted | |
| 1111 | + * @param leftmost indicates if this part is the leftmost in the range | |
| 1112 | + */ | |
| 1113 | + private static void sort(short[] a, int left, int right, boolean leftmost) { | |
| 1114 | + int length = right - left + 1; | |
| 1115 | + | |
| 1116 | + // Use insertion sort on tiny arrays | |
| 1117 | + if (length < INSERTION_SORT_THRESHOLD) { | |
| 1118 | + if (leftmost) { | |
| 1119 | + /* | |
| 1120 | + * Traditional (without sentinel) insertion sort, | |
| 1121 | + * optimized for server VM, is used in case of | |
| 1122 | + * the leftmost part. | |
| 1123 | + */ | |
| 1124 | + for (int i = left, j = i; i < right; j = ++i) { | |
| 1125 | + short ai = a[i + 1]; | |
| 1126 | + while (ai < a[j]) { | |
| 1127 | + a[j + 1] = a[j]; | |
| 1128 | + if (j-- == left) { | |
| 1129 | + break; | |
| 1130 | + } | |
| 1131 | + } | |
| 1132 | + a[j + 1] = ai; | |
| 1133 | + } | |
| 1134 | + } else { | |
| 1135 | + /* | |
| 1136 | + * Skip the longest ascending sequence. | |
| 1137 | + */ | |
| 1138 | + do { | |
| 1139 | + if (left >= right) { | |
| 1140 | + return; | |
| 1141 | + } | |
| 1142 | + } while (a[++left] >= a[left - 1]); | |
| 1143 | + | |
| 1144 | + /* | |
| 1145 | + * Every element from adjoining part plays the role | |
| 1146 | + * of sentinel, therefore this allows us to avoid the | |
| 1147 | + * left range check on each iteration. Moreover, we use | |
| 1148 | + * the more optimized algorithm, so called pair insertion | |
| 1149 | + * sort, which is faster (in the context of Quicksort) | |
| 1150 | + * than traditional implementation of insertion sort. | |
| 1151 | + */ | |
| 1152 | + for (int k = left; ++left <= right; k = ++left) { | |
| 1153 | + short a1 = a[k], a2 = a[left]; | |
| 1154 | + | |
| 1155 | + if (a1 < a2) { | |
| 1156 | + a2 = a1; a1 = a[left]; | |
| 1157 | + } | |
| 1158 | + while (a1 < a[--k]) { | |
| 1159 | + a[k + 2] = a[k]; | |
| 1160 | + } | |
| 1161 | + a[++k + 1] = a1; | |
| 1162 | + | |
| 1163 | + while (a2 < a[--k]) { | |
| 1164 | + a[k + 1] = a[k]; | |
| 1165 | + } | |
| 1166 | + a[k + 1] = a2; | |
| 1167 | + } | |
| 1168 | + short last = a[right]; | |
| 1169 | + | |
| 1170 | + while (last < a[--right]) { | |
| 1171 | + a[right + 1] = a[right]; | |
| 1172 | + } | |
| 1173 | + a[right + 1] = last; | |
| 1174 | + } | |
| 1175 | + return; | |
| 1176 | + } | |
| 1177 | + | |
| 1178 | + // Inexpensive approximation of length / 7 | |
| 1179 | + int seventh = (length >> 3) + (length >> 6) + 1; | |
| 1180 | + | |
| 1181 | + /* | |
| 1182 | + * Sort five evenly spaced elements around (and including) the | |
| 1183 | + * center element in the range. These elements will be used for | |
| 1184 | + * pivot selection as described below. The choice for spacing | |
| 1185 | + * these elements was empirically determined to work well on | |
| 1186 | + * a wide variety of inputs. | |
| 1187 | + */ | |
| 1188 | + int e3 = (left + right) >>> 1; // The midpoint | |
| 1189 | + int e2 = e3 - seventh; | |
| 1190 | + int e1 = e2 - seventh; | |
| 1191 | + int e4 = e3 + seventh; | |
| 1192 | + int e5 = e4 + seventh; | |
| 1193 | + | |
| 1194 | + // Sort these elements using insertion sort | |
| 1195 | + if (a[e2] < a[e1]) { short t = a[e2]; a[e2] = a[e1]; a[e1] = t; } | |
| 1196 | + | |
| 1197 | + if (a[e3] < a[e2]) { short t = a[e3]; a[e3] = a[e2]; a[e2] = t; | |
| 1198 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 1199 | + } | |
| 1200 | + if (a[e4] < a[e3]) { short t = a[e4]; a[e4] = a[e3]; a[e3] = t; | |
| 1201 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 1202 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 1203 | + } | |
| 1204 | + } | |
| 1205 | + if (a[e5] < a[e4]) { short t = a[e5]; a[e5] = a[e4]; a[e4] = t; | |
| 1206 | + if (t < a[e3]) { a[e4] = a[e3]; a[e3] = t; | |
| 1207 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 1208 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 1209 | + } | |
| 1210 | + } | |
| 1211 | + } | |
| 1212 | + | |
| 1213 | + // Pointers | |
| 1214 | + int less = left; // The index of the first element of center part | |
| 1215 | + int great = right; // The index before the first element of right part | |
| 1216 | + | |
| 1217 | + if (a[e1] != a[e2] && a[e2] != a[e3] && a[e3] != a[e4] && a[e4] != a[e5]) { | |
| 1218 | + /* | |
| 1219 | + * Use the second and fourth of the five sorted elements as pivots. | |
| 1220 | + * These values are inexpensive approximations of the first and | |
| 1221 | + * second terciles of the array. Note that pivot1 <= pivot2. | |
| 1222 | + */ | |
| 1223 | + short pivot1 = a[e2]; | |
| 1224 | + short pivot2 = a[e4]; | |
| 1225 | + | |
| 1226 | + /* | |
| 1227 | + * The first and the last elements to be sorted are moved to the | |
| 1228 | + * locations formerly occupied by the pivots. When partitioning | |
| 1229 | + * is complete, the pivots are swapped back into their final | |
| 1230 | + * positions, and excluded from subsequent sorting. | |
| 1231 | + */ | |
| 1232 | + a[e2] = a[left]; | |
| 1233 | + a[e4] = a[right]; | |
| 1234 | + | |
| 1235 | + /* | |
| 1236 | + * Skip elements, which are less or greater than pivot values. | |
| 1237 | + */ | |
| 1238 | + while (a[++less] < pivot1); | |
| 1239 | + while (a[--great] > pivot2); | |
| 1240 | + | |
| 1241 | + /* | |
| 1242 | + * Partitioning: | |
| 1243 | + * | |
| 1244 | + * left part center part right part | |
| 1245 | + * +--------------------------------------------------------------+ | |
| 1246 | + * | < pivot1 | pivot1 <= && <= pivot2 | ? | > pivot2 | | |
| 1247 | + * +--------------------------------------------------------------+ | |
| 1248 | + * ^ ^ ^ | |
| 1249 | + * | | | | |
| 1250 | + * less k great | |
| 1251 | + * | |
| 1252 | + * Invariants: | |
| 1253 | + * | |
| 1254 | + * all in (left, less) < pivot1 | |
| 1255 | + * pivot1 <= all in [less, k) <= pivot2 | |
| 1256 | + * all in (great, right) > pivot2 | |
| 1257 | + * | |
| 1258 | + * Pointer k is the first index of ?-part. | |
| 1259 | + */ | |
| 1260 | + outer: | |
| 1261 | + for (int k = less - 1; ++k <= great; ) { | |
| 1262 | + short ak = a[k]; | |
| 1263 | + if (ak < pivot1) { // Move a[k] to left part | |
| 1264 | + a[k] = a[less]; | |
| 1265 | + /* | |
| 1266 | + * Here and below we use "a[i] = b; i++;" instead | |
| 1267 | + * of "a[i++] = b;" due to performance issue. | |
| 1268 | + */ | |
| 1269 | + a[less] = ak; | |
| 1270 | + ++less; | |
| 1271 | + } else if (ak > pivot2) { // Move a[k] to right part | |
| 1272 | + while (a[great] > pivot2) { | |
| 1273 | + if (great-- == k) { | |
| 1274 | + break outer; | |
| 1275 | + } | |
| 1276 | + } | |
| 1277 | + if (a[great] < pivot1) { // a[great] <= pivot2 | |
| 1278 | + a[k] = a[less]; | |
| 1279 | + a[less] = a[great]; | |
| 1280 | + ++less; | |
| 1281 | + } else { // pivot1 <= a[great] <= pivot2 | |
| 1282 | + a[k] = a[great]; | |
| 1283 | + } | |
| 1284 | + /* | |
| 1285 | + * Here and below we use "a[i] = b; i--;" instead | |
| 1286 | + * of "a[i--] = b;" due to performance issue. | |
| 1287 | + */ | |
| 1288 | + a[great] = ak; | |
| 1289 | + --great; | |
| 1290 | + } | |
| 1291 | + } | |
| 1292 | + | |
| 1293 | + // Swap pivots into their final positions | |
| 1294 | + a[left] = a[less - 1]; a[less - 1] = pivot1; | |
| 1295 | + a[right] = a[great + 1]; a[great + 1] = pivot2; | |
| 1296 | + | |
| 1297 | + // Sort left and right parts recursively, excluding known pivots | |
| 1298 | + sort(a, left, less - 2, leftmost); | |
| 1299 | + sort(a, great + 2, right, false); | |
| 1300 | + | |
| 1301 | + /* | |
| 1302 | + * If center part is too large (comprises > 4/7 of the array), | |
| 1303 | + * swap internal pivot values to ends. | |
| 1304 | + */ | |
| 1305 | + if (less < e1 && e5 < great) { | |
| 1306 | + /* | |
| 1307 | + * Skip elements, which are equal to pivot values. | |
| 1308 | + */ | |
| 1309 | + while (a[less] == pivot1) { | |
| 1310 | + ++less; | |
| 1311 | + } | |
| 1312 | + | |
| 1313 | + while (a[great] == pivot2) { | |
| 1314 | + --great; | |
| 1315 | + } | |
| 1316 | + | |
| 1317 | + /* | |
| 1318 | + * Partitioning: | |
| 1319 | + * | |
| 1320 | + * left part center part right part | |
| 1321 | + * +----------------------------------------------------------+ | |
| 1322 | + * | == pivot1 | pivot1 < && < pivot2 | ? | == pivot2 | | |
| 1323 | + * +----------------------------------------------------------+ | |
| 1324 | + * ^ ^ ^ | |
| 1325 | + * | | | | |
| 1326 | + * less k great | |
| 1327 | + * | |
| 1328 | + * Invariants: | |
| 1329 | + * | |
| 1330 | + * all in (*, less) == pivot1 | |
| 1331 | + * pivot1 < all in [less, k) < pivot2 | |
| 1332 | + * all in (great, *) == pivot2 | |
| 1333 | + * | |
| 1334 | + * Pointer k is the first index of ?-part. | |
| 1335 | + */ | |
| 1336 | + outer: | |
| 1337 | + for (int k = less - 1; ++k <= great; ) { | |
| 1338 | + short ak = a[k]; | |
| 1339 | + if (ak == pivot1) { // Move a[k] to left part | |
| 1340 | + a[k] = a[less]; | |
| 1341 | + a[less] = ak; | |
| 1342 | + ++less; | |
| 1343 | + } else if (ak == pivot2) { // Move a[k] to right part | |
| 1344 | + while (a[great] == pivot2) { | |
| 1345 | + if (great-- == k) { | |
| 1346 | + break outer; | |
| 1347 | + } | |
| 1348 | + } | |
| 1349 | + if (a[great] == pivot1) { // a[great] < pivot2 | |
| 1350 | + a[k] = a[less]; | |
| 1351 | + /* | |
| 1352 | + * Even though a[great] equals to pivot1, the | |
| 1353 | + * assignment a[less] = pivot1 may be incorrect, | |
| 1354 | + * if a[great] and pivot1 are floating-point zeros | |
| 1355 | + * of different signs. Therefore in float and | |
| 1356 | + * double sorting methods we have to use more | |
| 1357 | + * accurate assignment a[less] = a[great]. | |
| 1358 | + */ | |
| 1359 | + a[less] = pivot1; | |
| 1360 | + ++less; | |
| 1361 | + } else { // pivot1 < a[great] < pivot2 | |
| 1362 | + a[k] = a[great]; | |
| 1363 | + } | |
| 1364 | + a[great] = ak; | |
| 1365 | + --great; | |
| 1366 | + } | |
| 1367 | + } | |
| 1368 | + } | |
| 1369 | + | |
| 1370 | + // Sort center part recursively | |
| 1371 | + sort(a, less, great, false); | |
| 1372 | + | |
| 1373 | + } else { // Partitioning with one pivot | |
| 1374 | + /* | |
| 1375 | + * Use the third of the five sorted elements as pivot. | |
| 1376 | + * This value is inexpensive approximation of the median. | |
| 1377 | + */ | |
| 1378 | + short pivot = a[e3]; | |
| 1379 | + | |
| 1380 | + /* | |
| 1381 | + * Partitioning degenerates to the traditional 3-way | |
| 1382 | + * (or "Dutch National Flag") schema: | |
| 1383 | + * | |
| 1384 | + * left part center part right part | |
| 1385 | + * +-------------------------------------------------+ | |
| 1386 | + * | < pivot | == pivot | ? | > pivot | | |
| 1387 | + * +-------------------------------------------------+ | |
| 1388 | + * ^ ^ ^ | |
| 1389 | + * | | | | |
| 1390 | + * less k great | |
| 1391 | + * | |
| 1392 | + * Invariants: | |
| 1393 | + * | |
| 1394 | + * all in (left, less) < pivot | |
| 1395 | + * all in [less, k) == pivot | |
| 1396 | + * all in (great, right) > pivot | |
| 1397 | + * | |
| 1398 | + * Pointer k is the first index of ?-part. | |
| 1399 | + */ | |
| 1400 | + for (int k = less; k <= great; ++k) { | |
| 1401 | + if (a[k] == pivot) { | |
| 1402 | + continue; | |
| 1403 | + } | |
| 1404 | + short ak = a[k]; | |
| 1405 | + if (ak < pivot) { // Move a[k] to left part | |
| 1406 | + a[k] = a[less]; | |
| 1407 | + a[less] = ak; | |
| 1408 | + ++less; | |
| 1409 | + } else { // a[k] > pivot - Move a[k] to right part | |
| 1410 | + while (a[great] > pivot) { | |
| 1411 | + --great; | |
| 1412 | + } | |
| 1413 | + if (a[great] < pivot) { // a[great] <= pivot | |
| 1414 | + a[k] = a[less]; | |
| 1415 | + a[less] = a[great]; | |
| 1416 | + ++less; | |
| 1417 | + } else { // a[great] == pivot | |
| 1418 | + /* | |
| 1419 | + * Even though a[great] equals to pivot, the | |
| 1420 | + * assignment a[k] = pivot may be incorrect, | |
| 1421 | + * if a[great] and pivot are floating-point | |
| 1422 | + * zeros of different signs. Therefore in float | |
| 1423 | + * and double sorting methods we have to use | |
| 1424 | + * more accurate assignment a[k] = a[great]. | |
| 1425 | + */ | |
| 1426 | + a[k] = pivot; | |
| 1427 | + } | |
| 1428 | + a[great] = ak; | |
| 1429 | + --great; | |
| 1430 | + } | |
| 1431 | + } | |
| 1432 | + | |
| 1433 | + /* | |
| 1434 | + * Sort left and right parts recursively. | |
| 1435 | + * All elements from center part are equal | |
| 1436 | + * and, therefore, already sorted. | |
| 1437 | + */ | |
| 1438 | + sort(a, left, less - 1, leftmost); | |
| 1439 | + sort(a, great + 1, right, false); | |
| 1440 | + } | |
| 1441 | + } | |
| 1442 | + | |
| 1443 | + /** | |
| 1444 | + * Sorts the specified array. | |
| 1445 | + * | |
| 1446 | + * @param a the array to be sorted | |
| 1447 | + */ | |
| 1448 | + public static void sort(char[] a) { | |
| 1449 | + sort(a, 0, a.length - 1); | |
| 1450 | + } | |
| 1451 | + | |
| 1452 | + /** | |
| 1453 | + * Sorts the specified range of the array. | |
| 1454 | + * | |
| 1455 | + * @param a the array to be sorted | |
| 1456 | + * @param left the index of the first element, inclusive, to be sorted | |
| 1457 | + * @param right the index of the last element, inclusive, to be sorted | |
| 1458 | + */ | |
| 1459 | + public static void sort(char[] a, int left, int right) { | |
| 1460 | + // Use counting sort on large arrays | |
| 1461 | + if (right - left > COUNTING_SORT_THRESHOLD_FOR_SHORT_OR_CHAR) { | |
| 1462 | + int[] count = new int[NUM_CHAR_VALUES]; | |
| 1463 | + | |
| 1464 | + for (int i = left - 1; ++i <= right; | |
| 1465 | + count[a[i]]++ | |
| 1466 | + ); | |
| 1467 | + for (int i = NUM_CHAR_VALUES, k = right + 1; k > left; ) { | |
| 1468 | + while (count[--i] == 0); | |
| 1469 | + char value = (char) i; | |
| 1470 | + int s = count[i]; | |
| 1471 | + | |
| 1472 | + do { | |
| 1473 | + a[--k] = value; | |
| 1474 | + } while (--s > 0); | |
| 1475 | + } | |
| 1476 | + } else { // Use Dual-Pivot Quicksort on small arrays | |
| 1477 | + doSort(a, left, right); | |
| 1478 | + } | |
| 1479 | + } | |
| 1480 | + | |
| 1481 | + /** The number of distinct char values. */ | |
| 1482 | + private static final int NUM_CHAR_VALUES = 1 << 16; | |
| 1483 | + | |
| 1484 | + /** | |
| 1485 | + * Sorts the specified range of the array. | |
| 1486 | + * | |
| 1487 | + * @param a the array to be sorted | |
| 1488 | + * @param left the index of the first element, inclusive, to be sorted | |
| 1489 | + * @param right the index of the last element, inclusive, to be sorted | |
| 1490 | + */ | |
| 1491 | + private static void doSort(char[] a, int left, int right) { | |
| 1492 | + // Use Quicksort on small arrays | |
| 1493 | + if (right - left < QUICKSORT_THRESHOLD) { | |
| 1494 | + sort(a, left, right, true); | |
| 1495 | + return; | |
| 1496 | + } | |
| 1497 | + | |
| 1498 | + /* | |
| 1499 | + * Index run[i] is the start of i-th run | |
| 1500 | + * (ascending or descending sequence). | |
| 1501 | + */ | |
| 1502 | + int[] run = new int[MAX_RUN_COUNT + 1]; | |
| 1503 | + int count = 0; run[0] = left; | |
| 1504 | + | |
| 1505 | + // Check if the array is nearly sorted | |
| 1506 | + for (int k = left; k < right; run[count] = k) { | |
| 1507 | + if (a[k] < a[k + 1]) { // ascending | |
| 1508 | + while (++k <= right && a[k - 1] <= a[k]); | |
| 1509 | + } else if (a[k] > a[k + 1]) { // descending | |
| 1510 | + while (++k <= right && a[k - 1] >= a[k]); | |
| 1511 | + for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) { | |
| 1512 | + char t = a[lo]; a[lo] = a[hi]; a[hi] = t; | |
| 1513 | + } | |
| 1514 | + } else { // equal | |
| 1515 | + for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) { | |
| 1516 | + if (--m == 0) { | |
| 1517 | + sort(a, left, right, true); | |
| 1518 | + return; | |
| 1519 | + } | |
| 1520 | + } | |
| 1521 | + } | |
| 1522 | + | |
| 1523 | + /* | |
| 1524 | + * The array is not highly structured, | |
| 1525 | + * use Quicksort instead of merge sort. | |
| 1526 | + */ | |
| 1527 | + if (++count == MAX_RUN_COUNT) { | |
| 1528 | + sort(a, left, right, true); | |
| 1529 | + return; | |
| 1530 | + } | |
| 1531 | + } | |
| 1532 | + | |
| 1533 | + // Check special cases | |
| 1534 | + if (run[count] == right++) { // The last run contains one element | |
| 1535 | + run[++count] = right; | |
| 1536 | + } else if (count == 1) { // The array is already sorted | |
| 1537 | + return; | |
| 1538 | + } | |
| 1539 | + | |
| 1540 | + /* | |
| 1541 | + * Create temporary array, which is used for merging. | |
| 1542 | + * Implementation note: variable "right" is increased by 1. | |
| 1543 | + */ | |
| 1544 | + char[] b; byte odd = 0; | |
| 1545 | + for (int n = 1; (n <<= 1) < count; odd ^= 1); | |
| 1546 | + | |
| 1547 | + if (odd == 0) { | |
| 1548 | + b = a; a = new char[b.length]; | |
| 1549 | + for (int i = left - 1; ++i < right; a[i] = b[i]); | |
| 1550 | + } else { | |
| 1551 | + b = new char[a.length]; | |
| 1552 | + } | |
| 1553 | + | |
| 1554 | + // Merging | |
| 1555 | + for (int last; count > 1; count = last) { | |
| 1556 | + for (int k = (last = 0) + 2; k <= count; k += 2) { | |
| 1557 | + int hi = run[k], mi = run[k - 1]; | |
| 1558 | + for (int i = run[k - 2], p = i, q = mi; i < hi; ++i) { | |
| 1559 | + if (q >= hi || p < mi && a[p] <= a[q]) { | |
| 1560 | + b[i] = a[p++]; | |
| 1561 | + } else { | |
| 1562 | + b[i] = a[q++]; | |
| 1563 | + } | |
| 1564 | + } | |
| 1565 | + run[++last] = hi; | |
| 1566 | + } | |
| 1567 | + if ((count & 1) != 0) { | |
| 1568 | + for (int i = right, lo = run[count - 1]; --i >= lo; | |
| 1569 | + b[i] = a[i] | |
| 1570 | + ); | |
| 1571 | + run[++last] = right; | |
| 1572 | + } | |
| 1573 | + char[] t = a; a = b; b = t; | |
| 1574 | + } | |
| 1575 | + } | |
| 1576 | + | |
| 1577 | + /** | |
| 1578 | + * Sorts the specified range of the array by Dual-Pivot Quicksort. | |
| 1579 | + * | |
| 1580 | + * @param a the array to be sorted | |
| 1581 | + * @param left the index of the first element, inclusive, to be sorted | |
| 1582 | + * @param right the index of the last element, inclusive, to be sorted | |
| 1583 | + * @param leftmost indicates if this part is the leftmost in the range | |
| 1584 | + */ | |
| 1585 | + private static void sort(char[] a, int left, int right, boolean leftmost) { | |
| 1586 | + int length = right - left + 1; | |
| 1587 | + | |
| 1588 | + // Use insertion sort on tiny arrays | |
| 1589 | + if (length < INSERTION_SORT_THRESHOLD) { | |
| 1590 | + if (leftmost) { | |
| 1591 | + /* | |
| 1592 | + * Traditional (without sentinel) insertion sort, | |
| 1593 | + * optimized for server VM, is used in case of | |
| 1594 | + * the leftmost part. | |
| 1595 | + */ | |
| 1596 | + for (int i = left, j = i; i < right; j = ++i) { | |
| 1597 | + char ai = a[i + 1]; | |
| 1598 | + while (ai < a[j]) { | |
| 1599 | + a[j + 1] = a[j]; | |
| 1600 | + if (j-- == left) { | |
| 1601 | + break; | |
| 1602 | + } | |
| 1603 | + } | |
| 1604 | + a[j + 1] = ai; | |
| 1605 | + } | |
| 1606 | + } else { | |
| 1607 | + /* | |
| 1608 | + * Skip the longest ascending sequence. | |
| 1609 | + */ | |
| 1610 | + do { | |
| 1611 | + if (left >= right) { | |
| 1612 | + return; | |
| 1613 | + } | |
| 1614 | + } while (a[++left] >= a[left - 1]); | |
| 1615 | + | |
| 1616 | + /* | |
| 1617 | + * Every element from adjoining part plays the role | |
| 1618 | + * of sentinel, therefore this allows us to avoid the | |
| 1619 | + * left range check on each iteration. Moreover, we use | |
| 1620 | + * the more optimized algorithm, so called pair insertion | |
| 1621 | + * sort, which is faster (in the context of Quicksort) | |
| 1622 | + * than traditional implementation of insertion sort. | |
| 1623 | + */ | |
| 1624 | + for (int k = left; ++left <= right; k = ++left) { | |
| 1625 | + char a1 = a[k], a2 = a[left]; | |
| 1626 | + | |
| 1627 | + if (a1 < a2) { | |
| 1628 | + a2 = a1; a1 = a[left]; | |
| 1629 | + } | |
| 1630 | + while (a1 < a[--k]) { | |
| 1631 | + a[k + 2] = a[k]; | |
| 1632 | + } | |
| 1633 | + a[++k + 1] = a1; | |
| 1634 | + | |
| 1635 | + while (a2 < a[--k]) { | |
| 1636 | + a[k + 1] = a[k]; | |
| 1637 | + } | |
| 1638 | + a[k + 1] = a2; | |
| 1639 | + } | |
| 1640 | + char last = a[right]; | |
| 1641 | + | |
| 1642 | + while (last < a[--right]) { | |
| 1643 | + a[right + 1] = a[right]; | |
| 1644 | + } | |
| 1645 | + a[right + 1] = last; | |
| 1646 | + } | |
| 1647 | + return; | |
| 1648 | + } | |
| 1649 | + | |
| 1650 | + // Inexpensive approximation of length / 7 | |
| 1651 | + int seventh = (length >> 3) + (length >> 6) + 1; | |
| 1652 | + | |
| 1653 | + /* | |
| 1654 | + * Sort five evenly spaced elements around (and including) the | |
| 1655 | + * center element in the range. These elements will be used for | |
| 1656 | + * pivot selection as described below. The choice for spacing | |
| 1657 | + * these elements was empirically determined to work well on | |
| 1658 | + * a wide variety of inputs. | |
| 1659 | + */ | |
| 1660 | + int e3 = (left + right) >>> 1; // The midpoint | |
| 1661 | + int e2 = e3 - seventh; | |
| 1662 | + int e1 = e2 - seventh; | |
| 1663 | + int e4 = e3 + seventh; | |
| 1664 | + int e5 = e4 + seventh; | |
| 1665 | + | |
| 1666 | + // Sort these elements using insertion sort | |
| 1667 | + if (a[e2] < a[e1]) { char t = a[e2]; a[e2] = a[e1]; a[e1] = t; } | |
| 1668 | + | |
| 1669 | + if (a[e3] < a[e2]) { char t = a[e3]; a[e3] = a[e2]; a[e2] = t; | |
| 1670 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 1671 | + } | |
| 1672 | + if (a[e4] < a[e3]) { char t = a[e4]; a[e4] = a[e3]; a[e3] = t; | |
| 1673 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 1674 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 1675 | + } | |
| 1676 | + } | |
| 1677 | + if (a[e5] < a[e4]) { char t = a[e5]; a[e5] = a[e4]; a[e4] = t; | |
| 1678 | + if (t < a[e3]) { a[e4] = a[e3]; a[e3] = t; | |
| 1679 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 1680 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 1681 | + } | |
| 1682 | + } | |
| 1683 | + } | |
| 1684 | + | |
| 1685 | + // Pointers | |
| 1686 | + int less = left; // The index of the first element of center part | |
| 1687 | + int great = right; // The index before the first element of right part | |
| 1688 | + | |
| 1689 | + if (a[e1] != a[e2] && a[e2] != a[e3] && a[e3] != a[e4] && a[e4] != a[e5]) { | |
| 1690 | + /* | |
| 1691 | + * Use the second and fourth of the five sorted elements as pivots. | |
| 1692 | + * These values are inexpensive approximations of the first and | |
| 1693 | + * second terciles of the array. Note that pivot1 <= pivot2. | |
| 1694 | + */ | |
| 1695 | + char pivot1 = a[e2]; | |
| 1696 | + char pivot2 = a[e4]; | |
| 1697 | + | |
| 1698 | + /* | |
| 1699 | + * The first and the last elements to be sorted are moved to the | |
| 1700 | + * locations formerly occupied by the pivots. When partitioning | |
| 1701 | + * is complete, the pivots are swapped back into their final | |
| 1702 | + * positions, and excluded from subsequent sorting. | |
| 1703 | + */ | |
| 1704 | + a[e2] = a[left]; | |
| 1705 | + a[e4] = a[right]; | |
| 1706 | + | |
| 1707 | + /* | |
| 1708 | + * Skip elements, which are less or greater than pivot values. | |
| 1709 | + */ | |
| 1710 | + while (a[++less] < pivot1); | |
| 1711 | + while (a[--great] > pivot2); | |
| 1712 | + | |
| 1713 | + /* | |
| 1714 | + * Partitioning: | |
| 1715 | + * | |
| 1716 | + * left part center part right part | |
| 1717 | + * +--------------------------------------------------------------+ | |
| 1718 | + * | < pivot1 | pivot1 <= && <= pivot2 | ? | > pivot2 | | |
| 1719 | + * +--------------------------------------------------------------+ | |
| 1720 | + * ^ ^ ^ | |
| 1721 | + * | | | | |
| 1722 | + * less k great | |
| 1723 | + * | |
| 1724 | + * Invariants: | |
| 1725 | + * | |
| 1726 | + * all in (left, less) < pivot1 | |
| 1727 | + * pivot1 <= all in [less, k) <= pivot2 | |
| 1728 | + * all in (great, right) > pivot2 | |
| 1729 | + * | |
| 1730 | + * Pointer k is the first index of ?-part. | |
| 1731 | + */ | |
| 1732 | + outer: | |
| 1733 | + for (int k = less - 1; ++k <= great; ) { | |
| 1734 | + char ak = a[k]; | |
| 1735 | + if (ak < pivot1) { // Move a[k] to left part | |
| 1736 | + a[k] = a[less]; | |
| 1737 | + /* | |
| 1738 | + * Here and below we use "a[i] = b; i++;" instead | |
| 1739 | + * of "a[i++] = b;" due to performance issue. | |
| 1740 | + */ | |
| 1741 | + a[less] = ak; | |
| 1742 | + ++less; | |
| 1743 | + } else if (ak > pivot2) { // Move a[k] to right part | |
| 1744 | + while (a[great] > pivot2) { | |
| 1745 | + if (great-- == k) { | |
| 1746 | + break outer; | |
| 1747 | + } | |
| 1748 | + } | |
| 1749 | + if (a[great] < pivot1) { // a[great] <= pivot2 | |
| 1750 | + a[k] = a[less]; | |
| 1751 | + a[less] = a[great]; | |
| 1752 | + ++less; | |
| 1753 | + } else { // pivot1 <= a[great] <= pivot2 | |
| 1754 | + a[k] = a[great]; | |
| 1755 | + } | |
| 1756 | + /* | |
| 1757 | + * Here and below we use "a[i] = b; i--;" instead | |
| 1758 | + * of "a[i--] = b;" due to performance issue. | |
| 1759 | + */ | |
| 1760 | + a[great] = ak; | |
| 1761 | + --great; | |
| 1762 | + } | |
| 1763 | + } | |
| 1764 | + | |
| 1765 | + // Swap pivots into their final positions | |
| 1766 | + a[left] = a[less - 1]; a[less - 1] = pivot1; | |
| 1767 | + a[right] = a[great + 1]; a[great + 1] = pivot2; | |
| 1768 | + | |
| 1769 | + // Sort left and right parts recursively, excluding known pivots | |
| 1770 | + sort(a, left, less - 2, leftmost); | |
| 1771 | + sort(a, great + 2, right, false); | |
| 1772 | + | |
| 1773 | + /* | |
| 1774 | + * If center part is too large (comprises > 4/7 of the array), | |
| 1775 | + * swap internal pivot values to ends. | |
| 1776 | + */ | |
| 1777 | + if (less < e1 && e5 < great) { | |
| 1778 | + /* | |
| 1779 | + * Skip elements, which are equal to pivot values. | |
| 1780 | + */ | |
| 1781 | + while (a[less] == pivot1) { | |
| 1782 | + ++less; | |
| 1783 | + } | |
| 1784 | + | |
| 1785 | + while (a[great] == pivot2) { | |
| 1786 | + --great; | |
| 1787 | + } | |
| 1788 | + | |
| 1789 | + /* | |
| 1790 | + * Partitioning: | |
| 1791 | + * | |
| 1792 | + * left part center part right part | |
| 1793 | + * +----------------------------------------------------------+ | |
| 1794 | + * | == pivot1 | pivot1 < && < pivot2 | ? | == pivot2 | | |
| 1795 | + * +----------------------------------------------------------+ | |
| 1796 | + * ^ ^ ^ | |
| 1797 | + * | | | | |
| 1798 | + * less k great | |
| 1799 | + * | |
| 1800 | + * Invariants: | |
| 1801 | + * | |
| 1802 | + * all in (*, less) == pivot1 | |
| 1803 | + * pivot1 < all in [less, k) < pivot2 | |
| 1804 | + * all in (great, *) == pivot2 | |
| 1805 | + * | |
| 1806 | + * Pointer k is the first index of ?-part. | |
| 1807 | + */ | |
| 1808 | + outer: | |
| 1809 | + for (int k = less - 1; ++k <= great; ) { | |
| 1810 | + char ak = a[k]; | |
| 1811 | + if (ak == pivot1) { // Move a[k] to left part | |
| 1812 | + a[k] = a[less]; | |
| 1813 | + a[less] = ak; | |
| 1814 | + ++less; | |
| 1815 | + } else if (ak == pivot2) { // Move a[k] to right part | |
| 1816 | + while (a[great] == pivot2) { | |
| 1817 | + if (great-- == k) { | |
| 1818 | + break outer; | |
| 1819 | + } | |
| 1820 | + } | |
| 1821 | + if (a[great] == pivot1) { // a[great] < pivot2 | |
| 1822 | + a[k] = a[less]; | |
| 1823 | + /* | |
| 1824 | + * Even though a[great] equals to pivot1, the | |
| 1825 | + * assignment a[less] = pivot1 may be incorrect, | |
| 1826 | + * if a[great] and pivot1 are floating-point zeros | |
| 1827 | + * of different signs. Therefore in float and | |
| 1828 | + * double sorting methods we have to use more | |
| 1829 | + * accurate assignment a[less] = a[great]. | |
| 1830 | + */ | |
| 1831 | + a[less] = pivot1; | |
| 1832 | + ++less; | |
| 1833 | + } else { // pivot1 < a[great] < pivot2 | |
| 1834 | + a[k] = a[great]; | |
| 1835 | + } | |
| 1836 | + a[great] = ak; | |
| 1837 | + --great; | |
| 1838 | + } | |
| 1839 | + } | |
| 1840 | + } | |
| 1841 | + | |
| 1842 | + // Sort center part recursively | |
| 1843 | + sort(a, less, great, false); | |
| 1844 | + | |
| 1845 | + } else { // Partitioning with one pivot | |
| 1846 | + /* | |
| 1847 | + * Use the third of the five sorted elements as pivot. | |
| 1848 | + * This value is inexpensive approximation of the median. | |
| 1849 | + */ | |
| 1850 | + char pivot = a[e3]; | |
| 1851 | + | |
| 1852 | + /* | |
| 1853 | + * Partitioning degenerates to the traditional 3-way | |
| 1854 | + * (or "Dutch National Flag") schema: | |
| 1855 | + * | |
| 1856 | + * left part center part right part | |
| 1857 | + * +-------------------------------------------------+ | |
| 1858 | + * | < pivot | == pivot | ? | > pivot | | |
| 1859 | + * +-------------------------------------------------+ | |
| 1860 | + * ^ ^ ^ | |
| 1861 | + * | | | | |
| 1862 | + * less k great | |
| 1863 | + * | |
| 1864 | + * Invariants: | |
| 1865 | + * | |
| 1866 | + * all in (left, less) < pivot | |
| 1867 | + * all in [less, k) == pivot | |
| 1868 | + * all in (great, right) > pivot | |
| 1869 | + * | |
| 1870 | + * Pointer k is the first index of ?-part. | |
| 1871 | + */ | |
| 1872 | + for (int k = less; k <= great; ++k) { | |
| 1873 | + if (a[k] == pivot) { | |
| 1874 | + continue; | |
| 1875 | + } | |
| 1876 | + char ak = a[k]; | |
| 1877 | + if (ak < pivot) { // Move a[k] to left part | |
| 1878 | + a[k] = a[less]; | |
| 1879 | + a[less] = ak; | |
| 1880 | + ++less; | |
| 1881 | + } else { // a[k] > pivot - Move a[k] to right part | |
| 1882 | + while (a[great] > pivot) { | |
| 1883 | + --great; | |
| 1884 | + } | |
| 1885 | + if (a[great] < pivot) { // a[great] <= pivot | |
| 1886 | + a[k] = a[less]; | |
| 1887 | + a[less] = a[great]; | |
| 1888 | + ++less; | |
| 1889 | + } else { // a[great] == pivot | |
| 1890 | + /* | |
| 1891 | + * Even though a[great] equals to pivot, the | |
| 1892 | + * assignment a[k] = pivot may be incorrect, | |
| 1893 | + * if a[great] and pivot are floating-point | |
| 1894 | + * zeros of different signs. Therefore in float | |
| 1895 | + * and double sorting methods we have to use | |
| 1896 | + * more accurate assignment a[k] = a[great]. | |
| 1897 | + */ | |
| 1898 | + a[k] = pivot; | |
| 1899 | + } | |
| 1900 | + a[great] = ak; | |
| 1901 | + --great; | |
| 1902 | + } | |
| 1903 | + } | |
| 1904 | + | |
| 1905 | + /* | |
| 1906 | + * Sort left and right parts recursively. | |
| 1907 | + * All elements from center part are equal | |
| 1908 | + * and, therefore, already sorted. | |
| 1909 | + */ | |
| 1910 | + sort(a, left, less - 1, leftmost); | |
| 1911 | + sort(a, great + 1, right, false); | |
| 1912 | + } | |
| 1913 | + } | |
| 1914 | + | |
| 1915 | + /** The number of distinct byte values. */ | |
| 1916 | + private static final int NUM_BYTE_VALUES = 1 << 8; | |
| 1917 | + | |
| 1918 | + /** | |
| 1919 | + * Sorts the specified array. | |
| 1920 | + * | |
| 1921 | + * @param a the array to be sorted | |
| 1922 | + */ | |
| 1923 | + public static void sort(byte[] a) { | |
| 1924 | + sort(a, 0, a.length - 1); | |
| 1925 | + } | |
| 1926 | + | |
| 1927 | + /** | |
| 1928 | + * Sorts the specified range of the array. | |
| 1929 | + * | |
| 1930 | + * @param a the array to be sorted | |
| 1931 | + * @param left the index of the first element, inclusive, to be sorted | |
| 1932 | + * @param right the index of the last element, inclusive, to be sorted | |
| 1933 | + */ | |
| 1934 | + public static void sort(byte[] a, int left, int right) { | |
| 1935 | + // Use counting sort on large arrays | |
| 1936 | + if (right - left > COUNTING_SORT_THRESHOLD_FOR_BYTE) { | |
| 1937 | + int[] count = new int[NUM_BYTE_VALUES]; | |
| 1938 | + | |
| 1939 | + for (int i = left - 1; ++i <= right; | |
| 1940 | + count[a[i] - Byte.MIN_VALUE]++ | |
| 1941 | + ); | |
| 1942 | + for (int i = NUM_BYTE_VALUES, k = right + 1; k > left; ) { | |
| 1943 | + while (count[--i] == 0); | |
| 1944 | + byte value = (byte) (i + Byte.MIN_VALUE); | |
| 1945 | + int s = count[i]; | |
| 1946 | + | |
| 1947 | + do { | |
| 1948 | + a[--k] = value; | |
| 1949 | + } while (--s > 0); | |
| 1950 | + } | |
| 1951 | + } else { // Use insertion sort on small arrays | |
| 1952 | + for (int i = left, j = i; i < right; j = ++i) { | |
| 1953 | + byte ai = a[i + 1]; | |
| 1954 | + while (ai < a[j]) { | |
| 1955 | + a[j + 1] = a[j]; | |
| 1956 | + if (j-- == left) { | |
| 1957 | + break; | |
| 1958 | + } | |
| 1959 | + } | |
| 1960 | + a[j + 1] = ai; | |
| 1961 | + } | |
| 1962 | + } | |
| 1963 | + } | |
| 1964 | + | |
| 1965 | + /** | |
| 1966 | + * Sorts the specified array. | |
| 1967 | + * | |
| 1968 | + * @param a the array to be sorted | |
| 1969 | + */ | |
| 1970 | + public static void sort(float[] a) { | |
| 1971 | + sort(a, 0, a.length - 1); | |
| 1972 | + } | |
| 1973 | + | |
| 1974 | + /** | |
| 1975 | + * Sorts the specified range of the array. | |
| 1976 | + * | |
| 1977 | + * @param a the array to be sorted | |
| 1978 | + * @param left the index of the first element, inclusive, to be sorted | |
| 1979 | + * @param right the index of the last element, inclusive, to be sorted | |
| 1980 | + */ | |
| 1981 | + public static void sort(float[] a, int left, int right) { | |
| 1982 | + /* | |
| 1983 | + * Phase 1: Move NaNs to the end of the array. | |
| 1984 | + */ | |
| 1985 | + while (left <= right && Float.isNaN(a[right])) { | |
| 1986 | + --right; | |
| 1987 | + } | |
| 1988 | + for (int k = right; --k >= left; ) { | |
| 1989 | + float ak = a[k]; | |
| 1990 | + if (ak != ak) { // a[k] is NaN | |
| 1991 | + a[k] = a[right]; | |
| 1992 | + a[right] = ak; | |
| 1993 | + --right; | |
| 1994 | + } | |
| 1995 | + } | |
| 1996 | + | |
| 1997 | + /* | |
| 1998 | + * Phase 2: Sort everything except NaNs (which are already in place). | |
| 1999 | + */ | |
| 2000 | + doSort(a, left, right); | |
| 2001 | + | |
| 2002 | + /* | |
| 2003 | + * Phase 3: Place negative zeros before positive zeros. | |
| 2004 | + */ | |
| 2005 | + int hi = right; | |
| 2006 | + | |
| 2007 | + /* | |
| 2008 | + * Find the first zero, or first positive, or last negative element. | |
| 2009 | + */ | |
| 2010 | + while (left < hi) { | |
| 2011 | + int middle = (left + hi) >>> 1; | |
| 2012 | + float middleValue = a[middle]; | |
| 2013 | + | |
| 2014 | + if (middleValue < 0.0f) { | |
| 2015 | + left = middle + 1; | |
| 2016 | + } else { | |
| 2017 | + hi = middle; | |
| 2018 | + } | |
| 2019 | + } | |
| 2020 | + | |
| 2021 | + /* | |
| 2022 | + * Skip the last negative value (if any) or all leading negative zeros. | |
| 2023 | + */ | |
| 2024 | + while (left <= right && Float.floatToRawIntBits(a[left]) < 0) { | |
| 2025 | + ++left; | |
| 2026 | + } | |
| 2027 | + | |
| 2028 | + /* | |
| 2029 | + * Move negative zeros to the beginning of the sub-range. | |
| 2030 | + * | |
| 2031 | + * Partitioning: | |
| 2032 | + * | |
| 2033 | + * +----------------------------------------------------+ | |
| 2034 | + * | < 0.0 | -0.0 | 0.0 | ? ( >= 0.0 ) | | |
| 2035 | + * +----------------------------------------------------+ | |
| 2036 | + * ^ ^ ^ | |
| 2037 | + * | | | | |
| 2038 | + * left p k | |
| 2039 | + * | |
| 2040 | + * Invariants: | |
| 2041 | + * | |
| 2042 | + * all in (*, left) < 0.0 | |
| 2043 | + * all in [left, p) == -0.0 | |
| 2044 | + * all in [p, k) == 0.0 | |
| 2045 | + * all in [k, right] >= 0.0 | |
| 2046 | + * | |
| 2047 | + * Pointer k is the first index of ?-part. | |
| 2048 | + */ | |
| 2049 | + for (int k = left, p = left - 1; ++k <= right; ) { | |
| 2050 | + float ak = a[k]; | |
| 2051 | + if (ak != 0.0f) { | |
| 2052 | + break; | |
| 2053 | + } | |
| 2054 | + if (Float.floatToRawIntBits(ak) < 0) { // ak is -0.0f | |
| 2055 | + a[k] = 0.0f; | |
| 2056 | + a[++p] = -0.0f; | |
| 2057 | + } | |
| 2058 | + } | |
| 2059 | + } | |
| 2060 | + | |
| 2061 | + /** | |
| 2062 | + * Sorts the specified range of the array. | |
| 2063 | + * | |
| 2064 | + * @param a the array to be sorted | |
| 2065 | + * @param left the index of the first element, inclusive, to be sorted | |
| 2066 | + * @param right the index of the last element, inclusive, to be sorted | |
| 2067 | + */ | |
| 2068 | + private static void doSort(float[] a, int left, int right) { | |
| 2069 | + // Use Quicksort on small arrays | |
| 2070 | + if (right - left < QUICKSORT_THRESHOLD) { | |
| 2071 | + sort(a, left, right, true); | |
| 2072 | + return; | |
| 2073 | + } | |
| 2074 | + | |
| 2075 | + /* | |
| 2076 | + * Index run[i] is the start of i-th run | |
| 2077 | + * (ascending or descending sequence). | |
| 2078 | + */ | |
| 2079 | + int[] run = new int[MAX_RUN_COUNT + 1]; | |
| 2080 | + int count = 0; run[0] = left; | |
| 2081 | + | |
| 2082 | + // Check if the array is nearly sorted | |
| 2083 | + for (int k = left; k < right; run[count] = k) { | |
| 2084 | + if (a[k] < a[k + 1]) { // ascending | |
| 2085 | + while (++k <= right && a[k - 1] <= a[k]); | |
| 2086 | + } else if (a[k] > a[k + 1]) { // descending | |
| 2087 | + while (++k <= right && a[k - 1] >= a[k]); | |
| 2088 | + for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) { | |
| 2089 | + float t = a[lo]; a[lo] = a[hi]; a[hi] = t; | |
| 2090 | + } | |
| 2091 | + } else { // equal | |
| 2092 | + for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) { | |
| 2093 | + if (--m == 0) { | |
| 2094 | + sort(a, left, right, true); | |
| 2095 | + return; | |
| 2096 | + } | |
| 2097 | + } | |
| 2098 | + } | |
| 2099 | + | |
| 2100 | + /* | |
| 2101 | + * The array is not highly structured, | |
| 2102 | + * use Quicksort instead of merge sort. | |
| 2103 | + */ | |
| 2104 | + if (++count == MAX_RUN_COUNT) { | |
| 2105 | + sort(a, left, right, true); | |
| 2106 | + return; | |
| 2107 | + } | |
| 2108 | + } | |
| 2109 | + | |
| 2110 | + // Check special cases | |
| 2111 | + if (run[count] == right++) { // The last run contains one element | |
| 2112 | + run[++count] = right; | |
| 2113 | + } else if (count == 1) { // The array is already sorted | |
| 2114 | + return; | |
| 2115 | + } | |
| 2116 | + | |
| 2117 | + /* | |
| 2118 | + * Create temporary array, which is used for merging. | |
| 2119 | + * Implementation note: variable "right" is increased by 1. | |
| 2120 | + */ | |
| 2121 | + float[] b; byte odd = 0; | |
| 2122 | + for (int n = 1; (n <<= 1) < count; odd ^= 1); | |
| 2123 | + | |
| 2124 | + if (odd == 0) { | |
| 2125 | + b = a; a = new float[b.length]; | |
| 2126 | + for (int i = left - 1; ++i < right; a[i] = b[i]); | |
| 2127 | + } else { | |
| 2128 | + b = new float[a.length]; | |
| 2129 | + } | |
| 2130 | + | |
| 2131 | + // Merging | |
| 2132 | + for (int last; count > 1; count = last) { | |
| 2133 | + for (int k = (last = 0) + 2; k <= count; k += 2) { | |
| 2134 | + int hi = run[k], mi = run[k - 1]; | |
| 2135 | + for (int i = run[k - 2], p = i, q = mi; i < hi; ++i) { | |
| 2136 | + if (q >= hi || p < mi && a[p] <= a[q]) { | |
| 2137 | + b[i] = a[p++]; | |
| 2138 | + } else { | |
| 2139 | + b[i] = a[q++]; | |
| 2140 | + } | |
| 2141 | + } | |
| 2142 | + run[++last] = hi; | |
| 2143 | + } | |
| 2144 | + if ((count & 1) != 0) { | |
| 2145 | + for (int i = right, lo = run[count - 1]; --i >= lo; | |
| 2146 | + b[i] = a[i] | |
| 2147 | + ); | |
| 2148 | + run[++last] = right; | |
| 2149 | + } | |
| 2150 | + float[] t = a; a = b; b = t; | |
| 2151 | + } | |
| 2152 | + } | |
| 2153 | + | |
| 2154 | + /** | |
| 2155 | + * Sorts the specified range of the array by Dual-Pivot Quicksort. | |
| 2156 | + * | |
| 2157 | + * @param a the array to be sorted | |
| 2158 | + * @param left the index of the first element, inclusive, to be sorted | |
| 2159 | + * @param right the index of the last element, inclusive, to be sorted | |
| 2160 | + * @param leftmost indicates if this part is the leftmost in the range | |
| 2161 | + */ | |
| 2162 | + private static void sort(float[] a, int left, int right, boolean leftmost) { | |
| 2163 | + int length = right - left + 1; | |
| 2164 | + | |
| 2165 | + // Use insertion sort on tiny arrays | |
| 2166 | + if (length < INSERTION_SORT_THRESHOLD) { | |
| 2167 | + if (leftmost) { | |
| 2168 | + /* | |
| 2169 | + * Traditional (without sentinel) insertion sort, | |
| 2170 | + * optimized for server VM, is used in case of | |
| 2171 | + * the leftmost part. | |
| 2172 | + */ | |
| 2173 | + for (int i = left, j = i; i < right; j = ++i) { | |
| 2174 | + float ai = a[i + 1]; | |
| 2175 | + while (ai < a[j]) { | |
| 2176 | + a[j + 1] = a[j]; | |
| 2177 | + if (j-- == left) { | |
| 2178 | + break; | |
| 2179 | + } | |
| 2180 | + } | |
| 2181 | + a[j + 1] = ai; | |
| 2182 | + } | |
| 2183 | + } else { | |
| 2184 | + /* | |
| 2185 | + * Skip the longest ascending sequence. | |
| 2186 | + */ | |
| 2187 | + do { | |
| 2188 | + if (left >= right) { | |
| 2189 | + return; | |
| 2190 | + } | |
| 2191 | + } while (a[++left] >= a[left - 1]); | |
| 2192 | + | |
| 2193 | + /* | |
| 2194 | + * Every element from adjoining part plays the role | |
| 2195 | + * of sentinel, therefore this allows us to avoid the | |
| 2196 | + * left range check on each iteration. Moreover, we use | |
| 2197 | + * the more optimized algorithm, so called pair insertion | |
| 2198 | + * sort, which is faster (in the context of Quicksort) | |
| 2199 | + * than traditional implementation of insertion sort. | |
| 2200 | + */ | |
| 2201 | + for (int k = left; ++left <= right; k = ++left) { | |
| 2202 | + float a1 = a[k], a2 = a[left]; | |
| 2203 | + | |
| 2204 | + if (a1 < a2) { | |
| 2205 | + a2 = a1; a1 = a[left]; | |
| 2206 | + } | |
| 2207 | + while (a1 < a[--k]) { | |
| 2208 | + a[k + 2] = a[k]; | |
| 2209 | + } | |
| 2210 | + a[++k + 1] = a1; | |
| 2211 | + | |
| 2212 | + while (a2 < a[--k]) { | |
| 2213 | + a[k + 1] = a[k]; | |
| 2214 | + } | |
| 2215 | + a[k + 1] = a2; | |
| 2216 | + } | |
| 2217 | + float last = a[right]; | |
| 2218 | + | |
| 2219 | + while (last < a[--right]) { | |
| 2220 | + a[right + 1] = a[right]; | |
| 2221 | + } | |
| 2222 | + a[right + 1] = last; | |
| 2223 | + } | |
| 2224 | + return; | |
| 2225 | + } | |
| 2226 | + | |
| 2227 | + // Inexpensive approximation of length / 7 | |
| 2228 | + int seventh = (length >> 3) + (length >> 6) + 1; | |
| 2229 | + | |
| 2230 | + /* | |
| 2231 | + * Sort five evenly spaced elements around (and including) the | |
| 2232 | + * center element in the range. These elements will be used for | |
| 2233 | + * pivot selection as described below. The choice for spacing | |
| 2234 | + * these elements was empirically determined to work well on | |
| 2235 | + * a wide variety of inputs. | |
| 2236 | + */ | |
| 2237 | + int e3 = (left + right) >>> 1; // The midpoint | |
| 2238 | + int e2 = e3 - seventh; | |
| 2239 | + int e1 = e2 - seventh; | |
| 2240 | + int e4 = e3 + seventh; | |
| 2241 | + int e5 = e4 + seventh; | |
| 2242 | + | |
| 2243 | + // Sort these elements using insertion sort | |
| 2244 | + if (a[e2] < a[e1]) { float t = a[e2]; a[e2] = a[e1]; a[e1] = t; } | |
| 2245 | + | |
| 2246 | + if (a[e3] < a[e2]) { float t = a[e3]; a[e3] = a[e2]; a[e2] = t; | |
| 2247 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 2248 | + } | |
| 2249 | + if (a[e4] < a[e3]) { float t = a[e4]; a[e4] = a[e3]; a[e3] = t; | |
| 2250 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 2251 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 2252 | + } | |
| 2253 | + } | |
| 2254 | + if (a[e5] < a[e4]) { float t = a[e5]; a[e5] = a[e4]; a[e4] = t; | |
| 2255 | + if (t < a[e3]) { a[e4] = a[e3]; a[e3] = t; | |
| 2256 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 2257 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 2258 | + } | |
| 2259 | + } | |
| 2260 | + } | |
| 2261 | + | |
| 2262 | + // Pointers | |
| 2263 | + int less = left; // The index of the first element of center part | |
| 2264 | + int great = right; // The index before the first element of right part | |
| 2265 | + | |
| 2266 | + if (a[e1] != a[e2] && a[e2] != a[e3] && a[e3] != a[e4] && a[e4] != a[e5]) { | |
| 2267 | + /* | |
| 2268 | + * Use the second and fourth of the five sorted elements as pivots. | |
| 2269 | + * These values are inexpensive approximations of the first and | |
| 2270 | + * second terciles of the array. Note that pivot1 <= pivot2. | |
| 2271 | + */ | |
| 2272 | + float pivot1 = a[e2]; | |
| 2273 | + float pivot2 = a[e4]; | |
| 2274 | + | |
| 2275 | + /* | |
| 2276 | + * The first and the last elements to be sorted are moved to the | |
| 2277 | + * locations formerly occupied by the pivots. When partitioning | |
| 2278 | + * is complete, the pivots are swapped back into their final | |
| 2279 | + * positions, and excluded from subsequent sorting. | |
| 2280 | + */ | |
| 2281 | + a[e2] = a[left]; | |
| 2282 | + a[e4] = a[right]; | |
| 2283 | + | |
| 2284 | + /* | |
| 2285 | + * Skip elements, which are less or greater than pivot values. | |
| 2286 | + */ | |
| 2287 | + while (a[++less] < pivot1); | |
| 2288 | + while (a[--great] > pivot2); | |
| 2289 | + | |
| 2290 | + /* | |
| 2291 | + * Partitioning: | |
| 2292 | + * | |
| 2293 | + * left part center part right part | |
| 2294 | + * +--------------------------------------------------------------+ | |
| 2295 | + * | < pivot1 | pivot1 <= && <= pivot2 | ? | > pivot2 | | |
| 2296 | + * +--------------------------------------------------------------+ | |
| 2297 | + * ^ ^ ^ | |
| 2298 | + * | | | | |
| 2299 | + * less k great | |
| 2300 | + * | |
| 2301 | + * Invariants: | |
| 2302 | + * | |
| 2303 | + * all in (left, less) < pivot1 | |
| 2304 | + * pivot1 <= all in [less, k) <= pivot2 | |
| 2305 | + * all in (great, right) > pivot2 | |
| 2306 | + * | |
| 2307 | + * Pointer k is the first index of ?-part. | |
| 2308 | + */ | |
| 2309 | + outer: | |
| 2310 | + for (int k = less - 1; ++k <= great; ) { | |
| 2311 | + float ak = a[k]; | |
| 2312 | + if (ak < pivot1) { // Move a[k] to left part | |
| 2313 | + a[k] = a[less]; | |
| 2314 | + /* | |
| 2315 | + * Here and below we use "a[i] = b; i++;" instead | |
| 2316 | + * of "a[i++] = b;" due to performance issue. | |
| 2317 | + */ | |
| 2318 | + a[less] = ak; | |
| 2319 | + ++less; | |
| 2320 | + } else if (ak > pivot2) { // Move a[k] to right part | |
| 2321 | + while (a[great] > pivot2) { | |
| 2322 | + if (great-- == k) { | |
| 2323 | + break outer; | |
| 2324 | + } | |
| 2325 | + } | |
| 2326 | + if (a[great] < pivot1) { // a[great] <= pivot2 | |
| 2327 | + a[k] = a[less]; | |
| 2328 | + a[less] = a[great]; | |
| 2329 | + ++less; | |
| 2330 | + } else { // pivot1 <= a[great] <= pivot2 | |
| 2331 | + a[k] = a[great]; | |
| 2332 | + } | |
| 2333 | + /* | |
| 2334 | + * Here and below we use "a[i] = b; i--;" instead | |
| 2335 | + * of "a[i--] = b;" due to performance issue. | |
| 2336 | + */ | |
| 2337 | + a[great] = ak; | |
| 2338 | + --great; | |
| 2339 | + } | |
| 2340 | + } | |
| 2341 | + | |
| 2342 | + // Swap pivots into their final positions | |
| 2343 | + a[left] = a[less - 1]; a[less - 1] = pivot1; | |
| 2344 | + a[right] = a[great + 1]; a[great + 1] = pivot2; | |
| 2345 | + | |
| 2346 | + // Sort left and right parts recursively, excluding known pivots | |
| 2347 | + sort(a, left, less - 2, leftmost); | |
| 2348 | + sort(a, great + 2, right, false); | |
| 2349 | + | |
| 2350 | + /* | |
| 2351 | + * If center part is too large (comprises > 4/7 of the array), | |
| 2352 | + * swap internal pivot values to ends. | |
| 2353 | + */ | |
| 2354 | + if (less < e1 && e5 < great) { | |
| 2355 | + /* | |
| 2356 | + * Skip elements, which are equal to pivot values. | |
| 2357 | + */ | |
| 2358 | + while (a[less] == pivot1) { | |
| 2359 | + ++less; | |
| 2360 | + } | |
| 2361 | + | |
| 2362 | + while (a[great] == pivot2) { | |
| 2363 | + --great; | |
| 2364 | + } | |
| 2365 | + | |
| 2366 | + /* | |
| 2367 | + * Partitioning: | |
| 2368 | + * | |
| 2369 | + * left part center part right part | |
| 2370 | + * +----------------------------------------------------------+ | |
| 2371 | + * | == pivot1 | pivot1 < && < pivot2 | ? | == pivot2 | | |
| 2372 | + * +----------------------------------------------------------+ | |
| 2373 | + * ^ ^ ^ | |
| 2374 | + * | | | | |
| 2375 | + * less k great | |
| 2376 | + * | |
| 2377 | + * Invariants: | |
| 2378 | + * | |
| 2379 | + * all in (*, less) == pivot1 | |
| 2380 | + * pivot1 < all in [less, k) < pivot2 | |
| 2381 | + * all in (great, *) == pivot2 | |
| 2382 | + * | |
| 2383 | + * Pointer k is the first index of ?-part. | |
| 2384 | + */ | |
| 2385 | + outer: | |
| 2386 | + for (int k = less - 1; ++k <= great; ) { | |
| 2387 | + float ak = a[k]; | |
| 2388 | + if (ak == pivot1) { // Move a[k] to left part | |
| 2389 | + a[k] = a[less]; | |
| 2390 | + a[less] = ak; | |
| 2391 | + ++less; | |
| 2392 | + } else if (ak == pivot2) { // Move a[k] to right part | |
| 2393 | + while (a[great] == pivot2) { | |
| 2394 | + if (great-- == k) { | |
| 2395 | + break outer; | |
| 2396 | + } | |
| 2397 | + } | |
| 2398 | + if (a[great] == pivot1) { // a[great] < pivot2 | |
| 2399 | + a[k] = a[less]; | |
| 2400 | + /* | |
| 2401 | + * Even though a[great] equals to pivot1, the | |
| 2402 | + * assignment a[less] = pivot1 may be incorrect, | |
| 2403 | + * if a[great] and pivot1 are floating-point zeros | |
| 2404 | + * of different signs. Therefore in float and | |
| 2405 | + * double sorting methods we have to use more | |
| 2406 | + * accurate assignment a[less] = a[great]. | |
| 2407 | + */ | |
| 2408 | + a[less] = a[great]; | |
| 2409 | + ++less; | |
| 2410 | + } else { // pivot1 < a[great] < pivot2 | |
| 2411 | + a[k] = a[great]; | |
| 2412 | + } | |
| 2413 | + a[great] = ak; | |
| 2414 | + --great; | |
| 2415 | + } | |
| 2416 | + } | |
| 2417 | + } | |
| 2418 | + | |
| 2419 | + // Sort center part recursively | |
| 2420 | + sort(a, less, great, false); | |
| 2421 | + | |
| 2422 | + } else { // Partitioning with one pivot | |
| 2423 | + /* | |
| 2424 | + * Use the third of the five sorted elements as pivot. | |
| 2425 | + * This value is inexpensive approximation of the median. | |
| 2426 | + */ | |
| 2427 | + float pivot = a[e3]; | |
| 2428 | + | |
| 2429 | + /* | |
| 2430 | + * Partitioning degenerates to the traditional 3-way | |
| 2431 | + * (or "Dutch National Flag") schema: | |
| 2432 | + * | |
| 2433 | + * left part center part right part | |
| 2434 | + * +-------------------------------------------------+ | |
| 2435 | + * | < pivot | == pivot | ? | > pivot | | |
| 2436 | + * +-------------------------------------------------+ | |
| 2437 | + * ^ ^ ^ | |
| 2438 | + * | | | | |
| 2439 | + * less k great | |
| 2440 | + * | |
| 2441 | + * Invariants: | |
| 2442 | + * | |
| 2443 | + * all in (left, less) < pivot | |
| 2444 | + * all in [less, k) == pivot | |
| 2445 | + * all in (great, right) > pivot | |
| 2446 | + * | |
| 2447 | + * Pointer k is the first index of ?-part. | |
| 2448 | + */ | |
| 2449 | + for (int k = less; k <= great; ++k) { | |
| 2450 | + if (a[k] == pivot) { | |
| 2451 | + continue; | |
| 2452 | + } | |
| 2453 | + float ak = a[k]; | |
| 2454 | + if (ak < pivot) { // Move a[k] to left part | |
| 2455 | + a[k] = a[less]; | |
| 2456 | + a[less] = ak; | |
| 2457 | + ++less; | |
| 2458 | + } else { // a[k] > pivot - Move a[k] to right part | |
| 2459 | + while (a[great] > pivot) { | |
| 2460 | + --great; | |
| 2461 | + } | |
| 2462 | + if (a[great] < pivot) { // a[great] <= pivot | |
| 2463 | + a[k] = a[less]; | |
| 2464 | + a[less] = a[great]; | |
| 2465 | + ++less; | |
| 2466 | + } else { // a[great] == pivot | |
| 2467 | + /* | |
| 2468 | + * Even though a[great] equals to pivot, the | |
| 2469 | + * assignment a[k] = pivot may be incorrect, | |
| 2470 | + * if a[great] and pivot are floating-point | |
| 2471 | + * zeros of different signs. Therefore in float | |
| 2472 | + * and double sorting methods we have to use | |
| 2473 | + * more accurate assignment a[k] = a[great]. | |
| 2474 | + */ | |
| 2475 | + a[k] = a[great]; | |
| 2476 | + } | |
| 2477 | + a[great] = ak; | |
| 2478 | + --great; | |
| 2479 | + } | |
| 2480 | + } | |
| 2481 | + | |
| 2482 | + /* | |
| 2483 | + * Sort left and right parts recursively. | |
| 2484 | + * All elements from center part are equal | |
| 2485 | + * and, therefore, already sorted. | |
| 2486 | + */ | |
| 2487 | + sort(a, left, less - 1, leftmost); | |
| 2488 | + sort(a, great + 1, right, false); | |
| 2489 | + } | |
| 2490 | + } | |
| 2491 | + | |
| 2492 | + /** | |
| 2493 | + * Sorts the specified array. | |
| 2494 | + * | |
| 2495 | + * @param a the array to be sorted | |
| 2496 | + */ | |
| 2497 | + public static void sort(double[] a) { | |
| 2498 | + sort(a, 0, a.length - 1); | |
| 2499 | + } | |
| 2500 | + | |
| 2501 | + /** | |
| 2502 | + * Sorts the specified range of the array. | |
| 2503 | + * | |
| 2504 | + * @param a the array to be sorted | |
| 2505 | + * @param left the index of the first element, inclusive, to be sorted | |
| 2506 | + * @param right the index of the last element, inclusive, to be sorted | |
| 2507 | + */ | |
| 2508 | + public static void sort(double[] a, int left, int right) { | |
| 2509 | + /* | |
| 2510 | + * Phase 1: Move NaNs to the end of the array. | |
| 2511 | + */ | |
| 2512 | + while (left <= right && Double.isNaN(a[right])) { | |
| 2513 | + --right; | |
| 2514 | + } | |
| 2515 | + for (int k = right; --k >= left; ) { | |
| 2516 | + double ak = a[k]; | |
| 2517 | + if (ak != ak) { // a[k] is NaN | |
| 2518 | + a[k] = a[right]; | |
| 2519 | + a[right] = ak; | |
| 2520 | + --right; | |
| 2521 | + } | |
| 2522 | + } | |
| 2523 | + | |
| 2524 | + /* | |
| 2525 | + * Phase 2: Sort everything except NaNs (which are already in place). | |
| 2526 | + */ | |
| 2527 | + doSort(a, left, right); | |
| 2528 | + | |
| 2529 | + /* | |
| 2530 | + * Phase 3: Place negative zeros before positive zeros. | |
| 2531 | + */ | |
| 2532 | + int hi = right; | |
| 2533 | + | |
| 2534 | + /* | |
| 2535 | + * Find the first zero, or first positive, or last negative element. | |
| 2536 | + */ | |
| 2537 | + while (left < hi) { | |
| 2538 | + int middle = (left + hi) >>> 1; | |
| 2539 | + double middleValue = a[middle]; | |
| 2540 | + | |
| 2541 | + if (middleValue < 0.0d) { | |
| 2542 | + left = middle + 1; | |
| 2543 | + } else { | |
| 2544 | + hi = middle; | |
| 2545 | + } | |
| 2546 | + } | |
| 2547 | + | |
| 2548 | + /* | |
| 2549 | + * Skip the last negative value (if any) or all leading negative zeros. | |
| 2550 | + */ | |
| 2551 | + while (left <= right && Double.doubleToRawLongBits(a[left]) < 0) { | |
| 2552 | + ++left; | |
| 2553 | + } | |
| 2554 | + | |
| 2555 | + /* | |
| 2556 | + * Move negative zeros to the beginning of the sub-range. | |
| 2557 | + * | |
| 2558 | + * Partitioning: | |
| 2559 | + * | |
| 2560 | + * +----------------------------------------------------+ | |
| 2561 | + * | < 0.0 | -0.0 | 0.0 | ? ( >= 0.0 ) | | |
| 2562 | + * +----------------------------------------------------+ | |
| 2563 | + * ^ ^ ^ | |
| 2564 | + * | | | | |
| 2565 | + * left p k | |
| 2566 | + * | |
| 2567 | + * Invariants: | |
| 2568 | + * | |
| 2569 | + * all in (*, left) < 0.0 | |
| 2570 | + * all in [left, p) == -0.0 | |
| 2571 | + * all in [p, k) == 0.0 | |
| 2572 | + * all in [k, right] >= 0.0 | |
| 2573 | + * | |
| 2574 | + * Pointer k is the first index of ?-part. | |
| 2575 | + */ | |
| 2576 | + for (int k = left, p = left - 1; ++k <= right; ) { | |
| 2577 | + double ak = a[k]; | |
| 2578 | + if (ak != 0.0d) { | |
| 2579 | + break; | |
| 2580 | + } | |
| 2581 | + if (Double.doubleToRawLongBits(ak) < 0) { // ak is -0.0d | |
| 2582 | + a[k] = 0.0d; | |
| 2583 | + a[++p] = -0.0d; | |
| 2584 | + } | |
| 2585 | + } | |
| 2586 | + } | |
| 2587 | + | |
| 2588 | + /** | |
| 2589 | + * Sorts the specified range of the array. | |
| 2590 | + * | |
| 2591 | + * @param a the array to be sorted | |
| 2592 | + * @param left the index of the first element, inclusive, to be sorted | |
| 2593 | + * @param right the index of the last element, inclusive, to be sorted | |
| 2594 | + */ | |
| 2595 | + private static void doSort(double[] a, int left, int right) { | |
| 2596 | + // Use Quicksort on small arrays | |
| 2597 | + if (right - left < QUICKSORT_THRESHOLD) { | |
| 2598 | + sort(a, left, right, true); | |
| 2599 | + return; | |
| 2600 | + } | |
| 2601 | + | |
| 2602 | + /* | |
| 2603 | + * Index run[i] is the start of i-th run | |
| 2604 | + * (ascending or descending sequence). | |
| 2605 | + */ | |
| 2606 | + int[] run = new int[MAX_RUN_COUNT + 1]; | |
| 2607 | + int count = 0; run[0] = left; | |
| 2608 | + | |
| 2609 | + // Check if the array is nearly sorted | |
| 2610 | + for (int k = left; k < right; run[count] = k) { | |
| 2611 | + if (a[k] < a[k + 1]) { // ascending | |
| 2612 | + while (++k <= right && a[k - 1] <= a[k]); | |
| 2613 | + } else if (a[k] > a[k + 1]) { // descending | |
| 2614 | + while (++k <= right && a[k - 1] >= a[k]); | |
| 2615 | + for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) { | |
| 2616 | + double t = a[lo]; a[lo] = a[hi]; a[hi] = t; | |
| 2617 | + } | |
| 2618 | + } else { // equal | |
| 2619 | + for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) { | |
| 2620 | + if (--m == 0) { | |
| 2621 | + sort(a, left, right, true); | |
| 2622 | + return; | |
| 2623 | + } | |
| 2624 | + } | |
| 2625 | + } | |
| 2626 | + | |
| 2627 | + /* | |
| 2628 | + * The array is not highly structured, | |
| 2629 | + * use Quicksort instead of merge sort. | |
| 2630 | + */ | |
| 2631 | + if (++count == MAX_RUN_COUNT) { | |
| 2632 | + sort(a, left, right, true); | |
| 2633 | + return; | |
| 2634 | + } | |
| 2635 | + } | |
| 2636 | + | |
| 2637 | + // Check special cases | |
| 2638 | + if (run[count] == right++) { // The last run contains one element | |
| 2639 | + run[++count] = right; | |
| 2640 | + } else if (count == 1) { // The array is already sorted | |
| 2641 | + return; | |
| 2642 | + } | |
| 2643 | + | |
| 2644 | + /* | |
| 2645 | + * Create temporary array, which is used for merging. | |
| 2646 | + * Implementation note: variable "right" is increased by 1. | |
| 2647 | + */ | |
| 2648 | + double[] b; byte odd = 0; | |
| 2649 | + for (int n = 1; (n <<= 1) < count; odd ^= 1); | |
| 2650 | + | |
| 2651 | + if (odd == 0) { | |
| 2652 | + b = a; a = new double[b.length]; | |
| 2653 | + for (int i = left - 1; ++i < right; a[i] = b[i]); | |
| 2654 | + } else { | |
| 2655 | + b = new double[a.length]; | |
| 2656 | + } | |
| 2657 | + | |
| 2658 | + // Merging | |
| 2659 | + for (int last; count > 1; count = last) { | |
| 2660 | + for (int k = (last = 0) + 2; k <= count; k += 2) { | |
| 2661 | + int hi = run[k], mi = run[k - 1]; | |
| 2662 | + for (int i = run[k - 2], p = i, q = mi; i < hi; ++i) { | |
| 2663 | + if (q >= hi || p < mi && a[p] <= a[q]) { | |
| 2664 | + b[i] = a[p++]; | |
| 2665 | + } else { | |
| 2666 | + b[i] = a[q++]; | |
| 2667 | + } | |
| 2668 | + } | |
| 2669 | + run[++last] = hi; | |
| 2670 | + } | |
| 2671 | + if ((count & 1) != 0) { | |
| 2672 | + for (int i = right, lo = run[count - 1]; --i >= lo; | |
| 2673 | + b[i] = a[i] | |
| 2674 | + ); | |
| 2675 | + run[++last] = right; | |
| 2676 | + } | |
| 2677 | + double[] t = a; a = b; b = t; | |
| 2678 | + } | |
| 2679 | + } | |
| 2680 | + | |
| 2681 | + /** | |
| 2682 | + * Sorts the specified range of the array by Dual-Pivot Quicksort. | |
| 2683 | + * | |
| 2684 | + * @param a the array to be sorted | |
| 2685 | + * @param left the index of the first element, inclusive, to be sorted | |
| 2686 | + * @param right the index of the last element, inclusive, to be sorted | |
| 2687 | + * @param leftmost indicates if this part is the leftmost in the range | |
| 2688 | + */ | |
| 2689 | + private static void sort(double[] a, int left, int right, boolean leftmost) { | |
| 2690 | + int length = right - left + 1; | |
| 2691 | + | |
| 2692 | + // Use insertion sort on tiny arrays | |
| 2693 | + if (length < INSERTION_SORT_THRESHOLD) { | |
| 2694 | + if (leftmost) { | |
| 2695 | + /* | |
| 2696 | + * Traditional (without sentinel) insertion sort, | |
| 2697 | + * optimized for server VM, is used in case of | |
| 2698 | + * the leftmost part. | |
| 2699 | + */ | |
| 2700 | + for (int i = left, j = i; i < right; j = ++i) { | |
| 2701 | + double ai = a[i + 1]; | |
| 2702 | + while (ai < a[j]) { | |
| 2703 | + a[j + 1] = a[j]; | |
| 2704 | + if (j-- == left) { | |
| 2705 | + break; | |
| 2706 | + } | |
| 2707 | + } | |
| 2708 | + a[j + 1] = ai; | |
| 2709 | + } | |
| 2710 | + } else { | |
| 2711 | + /* | |
| 2712 | + * Skip the longest ascending sequence. | |
| 2713 | + */ | |
| 2714 | + do { | |
| 2715 | + if (left >= right) { | |
| 2716 | + return; | |
| 2717 | + } | |
| 2718 | + } while (a[++left] >= a[left - 1]); | |
| 2719 | + | |
| 2720 | + /* | |
| 2721 | + * Every element from adjoining part plays the role | |
| 2722 | + * of sentinel, therefore this allows us to avoid the | |
| 2723 | + * left range check on each iteration. Moreover, we use | |
| 2724 | + * the more optimized algorithm, so called pair insertion | |
| 2725 | + * sort, which is faster (in the context of Quicksort) | |
| 2726 | + * than traditional implementation of insertion sort. | |
| 2727 | + */ | |
| 2728 | + for (int k = left; ++left <= right; k = ++left) { | |
| 2729 | + double a1 = a[k], a2 = a[left]; | |
| 2730 | + | |
| 2731 | + if (a1 < a2) { | |
| 2732 | + a2 = a1; a1 = a[left]; | |
| 2733 | + } | |
| 2734 | + while (a1 < a[--k]) { | |
| 2735 | + a[k + 2] = a[k]; | |
| 2736 | + } | |
| 2737 | + a[++k + 1] = a1; | |
| 2738 | + | |
| 2739 | + while (a2 < a[--k]) { | |
| 2740 | + a[k + 1] = a[k]; | |
| 2741 | + } | |
| 2742 | + a[k + 1] = a2; | |
| 2743 | + } | |
| 2744 | + double last = a[right]; | |
| 2745 | + | |
| 2746 | + while (last < a[--right]) { | |
| 2747 | + a[right + 1] = a[right]; | |
| 2748 | + } | |
| 2749 | + a[right + 1] = last; | |
| 2750 | + } | |
| 2751 | + return; | |
| 2752 | + } | |
| 2753 | + | |
| 2754 | + // Inexpensive approximation of length / 7 | |
| 2755 | + int seventh = (length >> 3) + (length >> 6) + 1; | |
| 2756 | + | |
| 2757 | + /* | |
| 2758 | + * Sort five evenly spaced elements around (and including) the | |
| 2759 | + * center element in the range. These elements will be used for | |
| 2760 | + * pivot selection as described below. The choice for spacing | |
| 2761 | + * these elements was empirically determined to work well on | |
| 2762 | + * a wide variety of inputs. | |
| 2763 | + */ | |
| 2764 | + int e3 = (left + right) >>> 1; // The midpoint | |
| 2765 | + int e2 = e3 - seventh; | |
| 2766 | + int e1 = e2 - seventh; | |
| 2767 | + int e4 = e3 + seventh; | |
| 2768 | + int e5 = e4 + seventh; | |
| 2769 | + | |
| 2770 | + // Sort these elements using insertion sort | |
| 2771 | + if (a[e2] < a[e1]) { double t = a[e2]; a[e2] = a[e1]; a[e1] = t; } | |
| 2772 | + | |
| 2773 | + if (a[e3] < a[e2]) { double t = a[e3]; a[e3] = a[e2]; a[e2] = t; | |
| 2774 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 2775 | + } | |
| 2776 | + if (a[e4] < a[e3]) { double t = a[e4]; a[e4] = a[e3]; a[e3] = t; | |
| 2777 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 2778 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 2779 | + } | |
| 2780 | + } | |
| 2781 | + if (a[e5] < a[e4]) { double t = a[e5]; a[e5] = a[e4]; a[e4] = t; | |
| 2782 | + if (t < a[e3]) { a[e4] = a[e3]; a[e3] = t; | |
| 2783 | + if (t < a[e2]) { a[e3] = a[e2]; a[e2] = t; | |
| 2784 | + if (t < a[e1]) { a[e2] = a[e1]; a[e1] = t; } | |
| 2785 | + } | |
| 2786 | + } | |
| 2787 | + } | |
| 2788 | + | |
| 2789 | + // Pointers | |
| 2790 | + int less = left; // The index of the first element of center part | |
| 2791 | + int great = right; // The index before the first element of right part | |
| 2792 | + | |
| 2793 | + if (a[e1] != a[e2] && a[e2] != a[e3] && a[e3] != a[e4] && a[e4] != a[e5]) { | |
| 2794 | + /* | |
| 2795 | + * Use the second and fourth of the five sorted elements as pivots. | |
| 2796 | + * These values are inexpensive approximations of the first and | |
| 2797 | + * second terciles of the array. Note that pivot1 <= pivot2. | |
| 2798 | + */ | |
| 2799 | + double pivot1 = a[e2]; | |
| 2800 | + double pivot2 = a[e4]; | |
| 2801 | + | |
| 2802 | + /* | |
| 2803 | + * The first and the last elements to be sorted are moved to the | |
| 2804 | + * locations formerly occupied by the pivots. When partitioning | |
| 2805 | + * is complete, the pivots are swapped back into their final | |
| 2806 | + * positions, and excluded from subsequent sorting. | |
| 2807 | + */ | |
| 2808 | + a[e2] = a[left]; | |
| 2809 | + a[e4] = a[right]; | |
| 2810 | + | |
| 2811 | + /* | |
| 2812 | + * Skip elements, which are less or greater than pivot values. | |
| 2813 | + */ | |
| 2814 | + while (a[++less] < pivot1); | |
| 2815 | + while (a[--great] > pivot2); | |
| 2816 | + | |
| 2817 | + /* | |
| 2818 | + * Partitioning: | |
| 2819 | + * | |
| 2820 | + * left part center part right part | |
| 2821 | + * +--------------------------------------------------------------+ | |
| 2822 | + * | < pivot1 | pivot1 <= && <= pivot2 | ? | > pivot2 | | |
| 2823 | + * +--------------------------------------------------------------+ | |
| 2824 | + * ^ ^ ^ | |
| 2825 | + * | | | | |
| 2826 | + * less k great | |
| 2827 | + * | |
| 2828 | + * Invariants: | |
| 2829 | + * | |
| 2830 | + * all in (left, less) < pivot1 | |
| 2831 | + * pivot1 <= all in [less, k) <= pivot2 | |
| 2832 | + * all in (great, right) > pivot2 | |
| 2833 | + * | |
| 2834 | + * Pointer k is the first index of ?-part. | |
| 2835 | + */ | |
| 2836 | + outer: | |
| 2837 | + for (int k = less - 1; ++k <= great; ) { | |
| 2838 | + double ak = a[k]; | |
| 2839 | + if (ak < pivot1) { // Move a[k] to left part | |
| 2840 | + a[k] = a[less]; | |
| 2841 | + /* | |
| 2842 | + * Here and below we use "a[i] = b; i++;" instead | |
| 2843 | + * of "a[i++] = b;" due to performance issue. | |
| 2844 | + */ | |
| 2845 | + a[less] = ak; | |
| 2846 | + ++less; | |
| 2847 | + } else if (ak > pivot2) { // Move a[k] to right part | |
| 2848 | + while (a[great] > pivot2) { | |
| 2849 | + if (great-- == k) { | |
| 2850 | + break outer; | |
| 2851 | + } | |
| 2852 | + } | |
| 2853 | + if (a[great] < pivot1) { // a[great] <= pivot2 | |
| 2854 | + a[k] = a[less]; | |
| 2855 | + a[less] = a[great]; | |
| 2856 | + ++less; | |
| 2857 | + } else { // pivot1 <= a[great] <= pivot2 | |
| 2858 | + a[k] = a[great]; | |
| 2859 | + } | |
| 2860 | + /* | |
| 2861 | + * Here and below we use "a[i] = b; i--;" instead | |
| 2862 | + * of "a[i--] = b;" due to performance issue. | |
| 2863 | + */ | |
| 2864 | + a[great] = ak; | |
| 2865 | + --great; | |
| 2866 | + } | |
| 2867 | + } | |
| 2868 | + | |
| 2869 | + // Swap pivots into their final positions | |
| 2870 | + a[left] = a[less - 1]; a[less - 1] = pivot1; | |
| 2871 | + a[right] = a[great + 1]; a[great + 1] = pivot2; | |
| 2872 | + | |
| 2873 | + // Sort left and right parts recursively, excluding known pivots | |
| 2874 | + sort(a, left, less - 2, leftmost); | |
| 2875 | + sort(a, great + 2, right, false); | |
| 2876 | + | |
| 2877 | + /* | |
| 2878 | + * If center part is too large (comprises > 4/7 of the array), | |
| 2879 | + * swap internal pivot values to ends. | |
| 2880 | + */ | |
| 2881 | + if (less < e1 && e5 < great) { | |
| 2882 | + /* | |
| 2883 | + * Skip elements, which are equal to pivot values. | |
| 2884 | + */ | |
| 2885 | + while (a[less] == pivot1) { | |
| 2886 | + ++less; | |
| 2887 | + } | |
| 2888 | + | |
| 2889 | + while (a[great] == pivot2) { | |
| 2890 | + --great; | |
| 2891 | + } | |
| 2892 | + | |
| 2893 | + /* | |
| 2894 | + * Partitioning: | |
| 2895 | + * | |
| 2896 | + * left part center part right part | |
| 2897 | + * +----------------------------------------------------------+ | |
| 2898 | + * | == pivot1 | pivot1 < && < pivot2 | ? | == pivot2 | | |
| 2899 | + * +----------------------------------------------------------+ | |
| 2900 | + * ^ ^ ^ | |
| 2901 | + * | | | | |
| 2902 | + * less k great | |
| 2903 | + * | |
| 2904 | + * Invariants: | |
| 2905 | + * | |
| 2906 | + * all in (*, less) == pivot1 | |
| 2907 | + * pivot1 < all in [less, k) < pivot2 | |
| 2908 | + * all in (great, *) == pivot2 | |
| 2909 | + * | |
| 2910 | + * Pointer k is the first index of ?-part. | |
| 2911 | + */ | |
| 2912 | + outer: | |
| 2913 | + for (int k = less - 1; ++k <= great; ) { | |
| 2914 | + double ak = a[k]; | |
| 2915 | + if (ak == pivot1) { // Move a[k] to left part | |
| 2916 | + a[k] = a[less]; | |
| 2917 | + a[less] = ak; | |
| 2918 | + ++less; | |
| 2919 | + } else if (ak == pivot2) { // Move a[k] to right part | |
| 2920 | + while (a[great] == pivot2) { | |
| 2921 | + if (great-- == k) { | |
| 2922 | + break outer; | |
| 2923 | + } | |
| 2924 | + } | |
| 2925 | + if (a[great] == pivot1) { // a[great] < pivot2 | |
| 2926 | + a[k] = a[less]; | |
| 2927 | + /* | |
| 2928 | + * Even though a[great] equals to pivot1, the | |
| 2929 | + * assignment a[less] = pivot1 may be incorrect, | |
| 2930 | + * if a[great] and pivot1 are floating-point zeros | |
| 2931 | + * of different signs. Therefore in float and | |
| 2932 | + * double sorting methods we have to use more | |
| 2933 | + * accurate assignment a[less] = a[great]. | |
| 2934 | + */ | |
| 2935 | + a[less] = a[great]; | |
| 2936 | + ++less; | |
| 2937 | + } else { // pivot1 < a[great] < pivot2 | |
| 2938 | + a[k] = a[great]; | |
| 2939 | + } | |
| 2940 | + a[great] = ak; | |
| 2941 | + --great; | |
| 2942 | + } | |
| 2943 | + } | |
| 2944 | + } | |
| 2945 | + | |
| 2946 | + // Sort center part recursively | |
| 2947 | + sort(a, less, great, false); | |
| 2948 | + | |
| 2949 | + } else { // Partitioning with one pivot | |
| 2950 | + /* | |
| 2951 | + * Use the third of the five sorted elements as pivot. | |
| 2952 | + * This value is inexpensive approximation of the median. | |
| 2953 | + */ | |
| 2954 | + double pivot = a[e3]; | |
| 2955 | + | |
| 2956 | + /* | |
| 2957 | + * Partitioning degenerates to the traditional 3-way | |
| 2958 | + * (or "Dutch National Flag") schema: | |
| 2959 | + * | |
| 2960 | + * left part center part right part | |
| 2961 | + * +-------------------------------------------------+ | |
| 2962 | + * | < pivot | == pivot | ? | > pivot | | |
| 2963 | + * +-------------------------------------------------+ | |
| 2964 | + * ^ ^ ^ | |
| 2965 | + * | | | | |
| 2966 | + * less k great | |
| 2967 | + * | |
| 2968 | + * Invariants: | |
| 2969 | + * | |
| 2970 | + * all in (left, less) < pivot | |
| 2971 | + * all in [less, k) == pivot | |
| 2972 | + * all in (great, right) > pivot | |
| 2973 | + * | |
| 2974 | + * Pointer k is the first index of ?-part. | |
| 2975 | + */ | |
| 2976 | + for (int k = less; k <= great; ++k) { | |
| 2977 | + if (a[k] == pivot) { | |
| 2978 | + continue; | |
| 2979 | + } | |
| 2980 | + double ak = a[k]; | |
| 2981 | + if (ak < pivot) { // Move a[k] to left part | |
| 2982 | + a[k] = a[less]; | |
| 2983 | + a[less] = ak; | |
| 2984 | + ++less; | |
| 2985 | + } else { // a[k] > pivot - Move a[k] to right part | |
| 2986 | + while (a[great] > pivot) { | |
| 2987 | + --great; | |
| 2988 | + } | |
| 2989 | + if (a[great] < pivot) { // a[great] <= pivot | |
| 2990 | + a[k] = a[less]; | |
| 2991 | + a[less] = a[great]; | |
| 2992 | + ++less; | |
| 2993 | + } else { // a[great] == pivot | |
| 2994 | + /* | |
| 2995 | + * Even though a[great] equals to pivot, the | |
| 2996 | + * assignment a[k] = pivot may be incorrect, | |
| 2997 | + * if a[great] and pivot are floating-point | |
| 2998 | + * zeros of different signs. Therefore in float | |
| 2999 | + * and double sorting methods we have to use | |
| 3000 | + * more accurate assignment a[k] = a[great]. | |
| 3001 | + */ | |
| 3002 | + a[k] = a[great]; | |
| 3003 | + } | |
| 3004 | + a[great] = ak; | |
| 3005 | + --great; | |
| 3006 | + } | |
| 3007 | + } | |
| 3008 | + | |
| 3009 | + /* | |
| 3010 | + * Sort left and right parts recursively. | |
| 3011 | + * All elements from center part are equal | |
| 3012 | + * and, therefore, already sorted. | |
| 3013 | + */ | |
| 3014 | + sort(a, left, less - 1, leftmost); | |
| 3015 | + sort(a, great + 1, right, false); | |
| 3016 | + } | |
| 3017 | + } | |
| 3018 | +} | |