基础算法：二维前缀和

二维前缀和思路

题目描述

参考代码

#include <iostream>

using namespace std;

const int N = 1010;

int n, m, q;
int a[N][N], s[N][N];

int main()
{
    scanf("%d%d%d", &n, &m, &q);
    
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
            scanf("%d", &a[i][j]);
    
    // 初始化前缀和数组
    for (int i = 1; i <= n; i++)
        for (int j  =1; j <= m; j++)
            s[i][j] = s[i - 1][j] +s[i][j - 1] - s[i - 1][j - 1] + a[i][j];
            
    // 询问
    while (q--)
    {
        int x1, y1, x2, y2;
        scanf("%d%d%d%d", &x1, &y1, &x2, &y2);
        cout << s[x2][y2] - s[x1 - 1][y2] - s[x2][y1 - 1] + s[x1 - 1][y1 - 1] << endl;
    }
    
    return 0;
}