poj1050(最大子矩阵和）

#include<cstdio>
#include<algorithm>
using namespace std;

const int nil=-(1<<29);
const int maxn=100;

int sum[maxn][maxn];

int main(){
    int n;
    scanf("%d",&n);
    int p;
    for (int i=1;i<=n;i++){
        for (int j=1;j<=n;j++){
            scanf("%d",&p);
            sum[i][j]=sum[i][j-1]+p;
        }
    }
    int ans=nil;
    for (int i=1;i<=n;i++){
        for (int j=i;j<=n;j++){
            int num=0;
            for (int k=1;k<=n;k++){
                if(num<0) num=0;
                num+=sum[k][j]-sum[k][i-1];
                ans=max(ans,num);
            }
        }
    }
    printf("%d\n",ans);
return 0;
}