【模板】树状数组

题意简述

已知一个数列，你需要进行下面两种操作：
1.将某一个数加上x
2.求出某区间每一个数的和

代码

#include <cstdio>
using namespace std;
int n, m;
int a[500001];
inline int lb(int x)
{
    return x & (-x);
}
void add(int x, int k)
{
    for (int i = x; i <= n; i += lb(i))
        a[i] += k;
}
int sum(int x)
{
    int ans = 0;
    for (int i = x; i; i -= lb(i))
        ans += a[i];
    return ans;
}
int main()
{
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; ++i)
    {
        int x;
        scanf("%d", &x);
        add(i, x);
    }
    for (int i = 1; i <= m; ++i)
    {
        int op, x, y;
        scanf("%d%d%d", &op, &x, &y);
        if (op == 1)
            add(x, y);
        else
            printf("%d
", sum(y) - sum(x - 1));
    }
}