树状数组裸题

直接进行树状数组即可，线段树当然也行（但是树状数组简单呀）

模板：

struct BIT {
    int tr[N];
    int lowbit(int x) { return x & (-x); }
    void modify(int x, int c) {
        for (; x <= n; x += lowbit(x)) {
            tr[x] += c;
        }
    }
    int check(int x) {
        int ans = 0;
        for (; x; x -= lowbit(x)) {
            ans += tr[x];
        };
        return ans;
    }
} TR;

之后就是这题代码了，，，

#include <bits/stdc++.h>
using namespace std;
const int N = 5e5 + 10;
int n, m, tmp, p;
char opt[2];
struct BIT {
    int tr[N];
    int lowbit(int x) { return x & (-x); }
    void modify(int x, int c) {
        for (; x <= n; x += lowbit(x)) {
            tr[x] += c;
        }
    }
    int check(int x) {
        int ans = 0;
        for (; x; x -= lowbit(x)) {
            ans += tr[x];
        };
        return ans;
    }
} TR;
int main() {
    scanf("%d%d", &n, &m);
    for (; m; m--) {
        scanf("%s", opt);
        if (*opt == 'A') {
            scanf("%d", &tmp);
            printf("%d\n", TR.check(tmp));
        } else if (*opt == 'B') {
            scanf("%d%d", &tmp, &p);
            TR.modify(tmp, p);
        } else {
            scanf("%d%d", &tmp, &p);
            TR.modify(tmp, -p);
        }
    }
    return 0;
}

ac记录（LOJ）：https://loj.ac/submission/850709