1002. 二哥种花生

容斥原理的简单应用

#include <bits/stdc++.h>
using namespace std;

#define maxn 1005

int d[maxn][maxn];

int main()
{
	int l,w;
	cin>>l>>w;
	
	memset(d,0,sizeof(d));
	
	for (int i=1;i<=l;i++){
		for (int j=1;j<=w;j++){
			cin>>d[i][j];
			d[i][j]=d[i][j]+d[i-1][j]+d[i][j-1]-d[i-1][j-1];
		}
	}
	
	int a,b;
	cin>>a>>b;
	
	int ans=0;
	for (int i=a;i<=l;i++){
		for (int j=b;j<=w;j++){
			ans=max(ans,  d[i][j]-d[i-a][j]-d[i][j-b]+d[i-a][j-b] );
		}
	}
	
	cout<<ans<<endl;
	
	
	return 0;
}