树状数组

描述

模版

struct binaryIndexedTree {
#define lowbit(x) ((x)&-(x))
int c[maxn];
void modify(int x, int v) {
for (int i = x; i <= maxn; i += lowbit(i))
c[i] += v;
}
int query(int x) {
int ret = 0;
for (int i = x; i > 0; i -= lowbit(i)) sum += c[i];
return ret;
}
};