largest_square.cpp

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

#define PI acos(-1)
#define pb push_back
#define int long long int
#define double long double
#define pi pair<int, int>
#define pii pair<pi, int>
#define fir first
#define sec second
#define MAXN 1001
#define mod 1000000007

signed main()
{
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n;
  cin >> n;
  int v[n][n];
  int dp[n][n];
  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++)
      cin >> v[i][j];
  int ans = 0;
  for (int i = 0; i < n; i++)
  {
    for (int j = 0; j < n; j++)
    {
      dp[i][j] = v[i][j];
      if (i && j && dp[i][j])
        dp[i][j] = min({dp[i][j - 1], dp[i - 1][j], dp[i - 1][j - 1]}) + 1;
      ans = max(ans, dp[i][j]);
    }
  }
  cout << ans * ans << endl;
  return 0;
}