前缀和、差分 复习

AcWing 796.子矩阵的和

#include <iostream>


using namespace std;
const int N = 1010;

int a[N][N];

int main()
{
    int n, m, q;
    cin >> n >> m >> q;

    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
        {
            cin >> a[i][j];
            a[i][j] += a[i - 1][j] + a[i][j - 1] - a[i - 1][j - 1]; // 3个
        }

    while (q--)
    {
        int x1, y1, x2, y2;
        cin >> x1 >> y1 >> x2 >> y2;

        int ans = a[x2][y2] - a[x1 - 1][y2] - a[x2][y1 - 1] + a[x1 - 1][y1 - 1]; // 3个

        cout << ans << endl;
    }

    return 0;
}