题解 | #【模板】前缀和#

#include <iostream>
using namespace std;

int main() 
{
    int n = 0;
    int q = 0;
    cin >> n >> q;
    int l = 0;
    int r = 0;
    long long arr[n];
    for (int i = 0; i < n && cin >> arr[i]; i++);
    for (int i = 1; i < n; i++)
    {
        arr[i] += arr[i - 1];
    }
    for (int i = 0; i < q && cin >> l >> r; i++)
    {
        if (l == 1)
        {
            cout << arr[r-1] << endl;
        }
        else 
        {
            cout << (arr[r-1] - arr[l-2]) << endl;
        }
        
    }
    return 0;
}