蜜汁90分WA第四点

500x500有点不太好调Ummmmmm

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;

template<typename Ty>void _read(Ty &x){
    Ty _num=0,_fac=1;
    char _peer=getchar();
    for(;!isdigit(_peer);_peer=getchar())if(_peer=='-')_fac=-1;
    for(;isdigit(_peer);_peer=getchar())_num=_num*10+_peer-'0';
    x=_fac*_num;
}

int n,m,a[2505][2505];
int f[2505][2505],s[2505][2505];

int main(){
    _read(n),_read(m);
    int ans=0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            _read(a[i][j]);
            s[i][j]=s[i-1][j]+s[i][j-1]-s[i-1][j-1]+a[i][j];
            if(a[i][j]>0&&s[i][j]-s[i-f[i-1][j-1]-1][j]-s[i][j-f[i-1][j-1]-1]+s[i-f[i-1][j-1]-1][j-f[i-1][j-1]-1]==f[i-1][j-1]+1)
                f[i][j]=f[i-1][j-1]+1;
            if(f[i][j]>ans)ans=f[i][j];
        }
    }

    for(int i=1;i<=n;i++){
        for(int j=m;j>=1;j--){
            s[i][j]=s[i-1][j]+s[i][j+1]-s[i-1][j+1]+a[i][j];
            if(a[i][j]>0&&s[i][j]-s[i-f[i-1][j+1]-1][j]-s[i][j+f[i-1][j+1]+1]+s[i-f[i-1][j+1]-1][j+f[i-1][j+1]+1]==f[i-1][j+1]+1)
                f[i][j]=f[i-1][j+1]+1;
            if(f[i][j]>ans)ans=f[i][j];
        }
    }

    printf("%d\n",ans);

    return 0;
}