区间修改 + 区间查询（树状数组）

结构：树状数组

参考博客：https://blog.csdn.net/zars19/article/details/54620021

题目：codev1082 线段树练习 3

http://codevs.cn/problem/1082/

代码：

#include <iostream>
#include <cstdio>

using namespace std;

#define lowbit(x) (x&(-x))

const int maxn = 2e5+7;

typedef long long ll;

ll sum[maxn];       //原始前缀和数组
ll delta[maxn];     //delta前缀和数组
ll delta_i[maxn];   //delta * i 前缀和数组
int n, m;

void update(ll *r, int x, int val) {
    for(int i = x; i <= n; i += lowbit(i)) {
        r[i] += val;
    }
}

ll query(ll *r, int x) {
    ll res = 0;
    for(int i = x; i > 0; i -= lowbit(i)) {
        res += r[i];
    }
    return res;
}

int main () {
    scanf("%d", &n);
    for(int i = 1;i <= n; i++) {
        scanf("%lld", &sum[i]);
        sum[i] += sum[i - 1];
    }
    scanf("%d", &m);
    while(m--) {
        int op, l, r, w;
        scanf("%d", &op);
        if(op == 1) {
            scanf("%d %d %d", &l, &r, &w);
            update(delta, l, w);
            update(delta, r + 1, -w);
            update(delta_i, l, l * w);
            update(delta_i, r + 1, (r + 1) * (-w));
        } else {
            scanf("%d %d", &l, &r);
            ll suml = sum[l - 1] + l * query(delta, l - 1) - query(delta_i, l - 1);     //这个是[1, left - 1]通过那个公式求出来得和
            ll sumr = sum[r] + (r + 1) * query(delta, r) - query(delta_i, r);           //这个是[1, right]通过那个公式求出来得和
            printf("%lld
", sumr - suml);
        }

    }
    return 0;
}