树状数组

#define lowbit(x) x&-x
//lowbit取二进制最后的10*序列（例：lowbit（1000100）= 100）
const int S;
int c[S] = {0};
void add(int x, int d){
    while(x <= S) c[x] += d,x += lowbit(x);
}
int sum(int x){
    int ret = 0;
    while(x > 0) ret += c[x], x -= lowbit(x);
    return ret;
}