POJ 3468 A Simple Problem with Integers?（线段树成段更新求和）

ACM

题目地址：POJ 3468 A Simple Problem with Integers?

题意： 
给出n个数，q个操作，'C'对区间每个数加值，'Q'查询区间和。

分析： 
裸的线段树成段更新。

代码：

/**  Author:      illuz <iilluzen[at]gmail.com>*  Blog:        http://blog.csdn.net/hcbbt*  File:        3468.cpp*  Create Date: 2014-08-08 15:53:07*  Descripton:  segment tree*/#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;#define repf(i,a,b) for(int i=(a);i<=(b);i++)#define lson(x) ((x) << 1)#define rson(x) ((x) << 1 | 1)typedef long long ll;const int N = 100100;const int ROOT = 1;struct seg {ll w;ll flag;};struct segment_tree {seg node[N << 2];void update(int pos) {node[pos].w = node[lson(pos)].w + node[rson(pos)].w;}void build(int l, int r, int pos) {node[pos].flag = 0;if (l == r) {scanf("%lld", &node[pos].w);return;}int m = (l + r) >> 1;build(l, m, lson(pos));build(m + 1, r, rson(pos));update(pos);}void push(int l, int r, int pos) {seg& fa = node[pos];seg& lhs = node[lson(pos)];seg& rhs = node[rson(pos)];int len = r - l + 1;if (fa.flag) {lhs.flag += fa.flag;rhs.flag += fa.flag;lhs.w += fa.flag * (len - (len >> 1));rhs.w += fa.flag * (len >> 1);fa.flag = 0;}}// add the point [x,y] with zvoid modify(int l, int r, int pos, int x, int y, ll z) {if (x <= l && r <= y) {int len = r + 1 - l;node[pos].w += z * len;node[pos].flag += z;return;}push(l, r, pos);int m = (l + r) >> 1;if (x <= m)modify(l, m, lson(pos), x, y, z);if (y > m)modify(m + 1, r, rson(pos), x, y, z);update(pos);}// query the segment [x, y]ll query(int l, int r, int pos, int x, int y) {if (x <= l && r <= y)return node[pos].w;push(l, r, pos);int m = (l + r) >> 1;ll res = 0;if (x <= m)res += query(l, m, lson(pos), x, y);if (y > m)res += query(m + 1, r, rson(pos), x, y);return res;}} sgm;int n, q, ra, rb;ll rc;char op[3];int main() {while (~scanf("%d%d", &n, &q)) {sgm.build(1, n, ROOT);while (q--) {scanf("%s", op);if (op[0] == 'Q') {scanf("%d%d", &ra, &rb);printf("%lld\n", sgm.query(1, n, ROOT, ra, rb));} else {scanf("%d%d%lld", &ra, &rb, &rc);sgm.modify(1, n, ROOT, ra, rb, rc);}}}return 0;}