BIT树状数组

#ifdef unix#define LLD "%lld"#else#define LLD "%I64d"#endif#include <cstdio>#include <cstring>#include <cstdlib>#include <cmath>#include <algorithm>#include <iostream>#include <vector>#include <stack>#include <queue>#include <map>#define LL long long#define maxn 100000#define INF 1 << 30#define For(i, n) for (int i = 1; i <= n; i++)#define rep(i, j, k) for (int i = j; i <= k; i++)#define lson l, mid, rt << 1#define rson mid + 1, r, rt << 1 | 1using namespace std;int n, m, a[maxn];struct BIT {int lowbit(int x) {return x & -x;}void modify(int x, int data) {while (x <= n) a[x] += data, x += lowbit(x);}int sum(int x) {int tot = 0;while (x > 0) tot+=a[x], x -= lowbit(x);return tot;}}bit;int main() {int x, y;memset(a, 0, sizeof(a));scanf("%d%d", &n, &m);For(i, n) {scanf("%d", &x);bit.modify(i, x);}For(i, m) {scanf("%d%d", &x, &y);printf("%d\n", bit.sum(y) - bit.sum(x - 1));}return 0;}