#include <u.h>#include <libc.h>#include <bst.h> typedef struct Intnode {	Bst;	int v;} Intnode; enum {	RED,	BLACK,	MAX =  1000000,	NODES = 100000}; Intnode pool[NODES]; intintcmp(Bst *a, Bst *b){	Intnode *an, *bn; 	an = (Intnode*)a;	bn = (Intnode*)b; 	if(an->v < bn->v)		return -1;	if(an->v > bn->v)		return 1;	return 0;}  voidblackbalance(Bst *h, int b, int *old){	if(h == nil) {		if(*old == 0)			*old = b;		else {			if(b != *old)				fprint(2, "black balance: %d %d\n", *old, b);			assert(b == *old);		}		return;	}	if(h->color == BLACK){		blackbalance(h->c[0], b+1, old);		blackbalance(h->c[1], b+1, old);	}else{		blackbalance(h->c[0], b, old);		blackbalance(h->c[0], b, old);	}} intcheckbalance(Bsttree *t){	int b; 	b = 0;	blackbalance(bstroot(t), 0, &b);	return b;} voidmain(void){	Bsttree *t;	Intnode *a, d;	int i, r; 	srand(time(nil));	t = bstcreatellrb(intcmp); 	for(a = pool; a < pool+nelem(pool); a++) {		a->v = nrand(MAX);		bstinsert(t, a);	}	checkbalance(t);	print("Balance is good after insertions.\n");	r = 0;	for(i = 0; i < NODES/2; i++) {		d.v = nrand(MAX);		a = (Intnode*)bstdelete(t, &d);		if(a != nil)			r++;	}	checkbalance(t);	print("Balance is good after %d deletions.\n", r);	exits(nil);}