20pts求调

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

const int N=111;
int a[N][N];
int b[N][N];

signed main()
{
//	freopen(".in","r",stdin);
//	freopen(".out","w",stdout);
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int n,m;
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=m;j++)
		{
			cin>>a[i][j];
		}
	}
	int ans=0;
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=m;j++)
		{
			b[i][j]=a[i][j]+a[i][j-1]+a[i-1][j]-a[i-1][j-1];
		}
	}
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=m;j++)
		{
			if(a[i][j]!=1)
			{
				continue;
			}
			for(int k=ans+1;i-k>=0&&j-k>=0;k++)
			{
				if(b[i][j]+b[i-k][j-k]-b[i-k][j]-b[i][j-k]==k*k)
				{
					ans=k;
				}
				else
				{
					break;
				}
			}
		}
	}
	cout<<ans;
	return 0;
}