题目描述

s[0] = 0
s[1] = a1
...
s[i] = a1 + a2 + ... + ai
=> al + ... + ar = s[r] - s[l - 1]

前缀和求长度为k的子段长度

样例

#include<iostream>

using namespace std;
const int N = 100010;

int s[N];
int n, m;


int main()
{
    cin >> n >> m;
    for (int i = 1; i <= n; i++){
        int x;
        cin >> x;
        s[i] = s[i - 1] + x;
    }
    for (int i = 0; i < m; i++){
        int l, r;
        cin >> l >> r;
        cout << s[r] - s[l - 1] << endl;
    }
    return 0;
}