python/TangDou/AcWing/BIT/P3374.md

## [$P3374$ 【模板】树状数组 1](https://www.luogu.com.cn/problem/P3374)

```cpp {.line-numbers}
#include <bits/stdc++.h>

using namespace std;
typedef long long LL;
const int N = 5 * 1e5 + 10;
int n, m;
int a[N];

// 树状数组模板
// 用while循环优于for循环，因为没有i变量，不易写错，代码更短
#define lowbit(x) (x & -x)
int c[N];
void add(int x, int v) {
    while (x < N) c[x] += v, x += lowbit(x);
}
LL sum(int x) {
    LL res = 0;
    while (x) res += c[x], x -= lowbit(x);
    return res;
}

int main() {
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
        cin >> a[i], add(i, a[i]); // 维护进入树状数组，两个概念：位置，值

    while (m--) {
        int op, x, y;
        cin >> op >> x >> y;
        if (op == 1)
            add(x, y); // 在x位置上加上y
        else
            // 计算[x,y]之间的数字和
            cout << sum(y) - sum(x - 1) << endl;
    }
    return 0;
}
```