_bzoj2002 [Hnoi2010]Bounce 弹飞绵羊【分块】

传送门：http://www.lydsy.com/JudgeOnline/problem.php?id=2002

见一周目记录：http://www.cnblogs.com/ciao-sora/p/6099077.html

#include <cstdio>
#include <cmath>

const int maxn = 200005;

int n, m, a[maxn], to[maxn], need[maxn], siz, id, t1, t2, t3, haji;

inline int qry(int pos) {
	int rt = 0;
	while (~pos) {
		rt += need[pos];
		pos = to[pos];
	}
	return rt;
}
inline void upd(int pos, int val) {
	id = pos / siz;
	haji = id * siz;
	a[pos] = val;
	for (int i = pos; i >= haji; --i) {
		if (i + a[i] >= n) {
			to[i] = -1;
			need[i] = 1;
		}
		else if (i + a[i] >= (id + 1) * siz) {
			to[i] = i + a[i];
			need[i] = 1;
		}
		else {
			to[i] = to[i + a[i]];
			need[i] = need[i + a[i]] + 1;
		}
	}
}

int main(void) {
	scanf("%d", &n);
	siz = (int)sqrt((float)n + 0.5f);
	for (int i = 0; i < n; ++i) {
		scanf("%d", a + i);
	}
	for (int i = n - 1; ~i; --i) {
		id = i / siz;
		if (i + a[i] >= n) {
			to[i] = -1;
			need[i] = 1;
		}
		else if (i + a[i] >= (id + 1) * siz) {
			to[i] = i + a[i];
			need[i] = 1;
		}
		else {
			to[i] = to[i + a[i]];
			need[i] = need[i + a[i]] + 1;
		}
	}
	scanf("%d", &m);
	while (m--) {
		scanf("%d%d", &t1, &t2);
		if (t1 == 1) {
			printf("%d\n", qry(t2));
		}
		else {
			scanf("%d", &t3);
			upd(t2, t3);
		}
	}
	return 0;
}