输入数据 循环时注意外层和内层的顺序(y x)
处理结果时r要从l开始

#include<cstdio>
#include<iostream>
using namespace std;
const int MAXN=2e2;

int a[MAXN][MAXN];//前缀和 
int n;

int main(){
    scanf("%d",&n);

    int ans=-2e9;
    bool isBigger=false;
    for(int y=1;y<=n;y++){
        for(int x=1;x<=n;x++){
            scanf("%d",&a[x][y]);
            ans=max(ans,a[x][y]);
            if(a[x][y]>0)isBigger=1;
            if(x!=1){
                a[x][y]+=a[x-1][y];//前缀和 
            }
        }
    }
    if(!isBigger){
        cout<<ans<<endl;
        return 0;
    }
    int nowAns=0;
    for(int l=1;l<=n;l++){
        for(int r=l;r<=n;r++){
            nowAns=0;
            for(int line=1;line<=n;line++){
                int tmp=a[r][line]-a[l-1][line];
                nowAns+=tmp;
                ans=max(ans,nowAns);
                if(nowAns<0)nowAns=0;
            }
        }
    }
    cout<<ans<<endl;
    return 0;
}