二维前缀和

https://www.acwing.com/problem/content/798/

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<iostream>
using namespace std;
int n, m, q;
const int N = 1010;
int a[N][N],s[N][N];

int main()
{
	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-1][j]+s[i][j-1]-s[i-1][j-1]+a[i][j];
		}
	while(q--)
	{
		int x1,y1,x2,y2;
		scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
		printf("%d\n",s[x2][y2]-s[x2][y1-1]-s[x1-1][y2]+s[x1-1][y1-1]);		
	}
	return 0;
}