4095번: 최대 정사각형 ↗

#include <bits/stdc++.h>

#define for1(s,n) for(int i = s; i < n; i++)
#define for1j(s,n) for(int j = s; j < n; j++)
#define foreach(k) for(auto i : k)
#define foreachj(k) for(auto j : k)
#define pb(a) push_back(a)
#define sz(a) a.size()

using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef vector <int> iv1;
typedef vector <vector<int>> iv2;
typedef vector <ll> llv1;
typedef unsigned int uint;
typedef vector <ull> ullv1;
typedef vector <vector <ull>> ullv2;

ll N,M;
ll ar[1100][1100];
ll D[1100][1100];

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
    while(true) {
        cin >> N >> M;
        if(N+M == 0) break;
        ll ans = 0;
        for1(0,N) {
            for1j(0,M) {
                cin >> ar[i][j];
                D[i][j] = ar[i][j];
                ans = max(ans, ar[i][j]);
            }
        }

        for1(1,N) {
            for1j(1,M) {
                if(ar[i][j] == 1) D[i][j] = min(D[i-1][j-1], min(D[i-1][j],D[i][j-1])) + 1;
                ans = max(ans,D[i][j]);
            }
        }
        cout << ans << "\n";


    }
    
}