蓝桥杯 - 操作格子 （线段树）

题目传送：操作格子

思路：简单线段树，单点更新，区间求和以及最值

AC代码：

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>#include <cmath>#include <queue>#include <stack>#include <vector>#include <map>#include <set>#include <deque>#include <cctype>#define LL long long#define INF 0x7fffffffusing namespace std;const int maxn = 100005;int n, m;int sum[maxn << 2], MAX[maxn << 2];void build(int l, int r, int rt) {if(l == r) {scanf("%d", &sum[rt]);MAX[rt] = sum[rt];return;}int mid = (l + r) >> 1;build(l, mid, rt << 1);build(mid + 1, r, rt << 1 | 1);sum[rt] = sum[rt << 1] + sum[rt << 1 | 1];MAX[rt] = max(MAX[rt << 1], MAX[rt << 1 | 1]);}void update(int p, int y, int l, int r, int rt) {if(l == r) {sum[rt] = y;MAX[rt] = y;return;}int mid = (l + r) >> 1;if(p <= mid) update(p, y, l, mid, rt << 1);else update(p, y, mid + 1, r, rt << 1 | 1);sum[rt] = sum[rt << 1] + sum[rt << 1 | 1];MAX[rt] = max(MAX[rt << 1], MAX[rt << 1 | 1]);}int query_sum(int L, int R, int l, int r, int rt) {if(L <= l && r <= R) {return sum[rt];}int mid = (l + r) >> 1;int ret = 0;if(L <= mid) ret += query_sum(L, R, l, mid, rt << 1);if(R >= mid + 1) ret += query_sum(L, R, mid + 1, r, rt << 1 | 1);return ret;}int query_MAX(int L, int R, int l, int r, int rt) {if(L <= l && r <= R) {return MAX[rt];}int mid = (l + r) >> 1;int ret = 0;if(L <= mid) ret = max(ret, query_MAX(L, R, l, mid, rt << 1));if(R >= mid + 1) ret = max(ret, query_MAX(L, R, mid + 1, r, rt << 1 | 1));return ret;}int main() {while(scanf("%d %d", &n, &m) != EOF) {build(1, n, 1);while(m --) {int p, x, y;scanf("%d %d %d", &p, &x, &y);if(p == 1) {update(x, y, 1, n, 1);}else if(p == 2) {printf("%d\n", query_sum(x, y, 1, n, 1));}else {printf("%d\n", query_MAX(x, y, 1, n, 1));}}}return 0;}