理解二维前缀和：

#include <iostream>using namespace std;const int N = 1010;int a[N][N], s[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++) {scanf("%d", &a[i][j]);s[i][j] = s[i][j - 1] + s[i - 1][j] - s[i - 1][j - 1] + a[i][j]; // 求前缀和}while (q--) {int x1,y1,x2,y2;scanf("%d%d%d%d", &x1, &y1, &x2, &y2);// 算子矩阵的和printf("%d\n", s[x2][y2] - s[x2][y1 - 1] - s[x1 - 1][y2] + s[x1 - 1][y1 - 1]);}return 0;
}