가장 큰 정사각형.java

import java.util.*;
import java.io.*;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		StringTokenizer st = new StringTokenizer(br.readLine());
		int n = Integer.parseInt(st.nextToken());
		int m = Integer.parseInt(st.nextToken());

		long [][] dp = new long[1001][1001];
		long max = 0;

		for(int i =0; i<n; i++) {
			String input = br.readLine();

			for(int j =0; j < m; j++) {
				dp[i][j] = Long.parseLong(String.valueOf(input.charAt(j)));

				if(dp[i][j] ==1 && j>0 && i>0) {
					dp[i][j] = Math.min(dp[i-1][j-1], Math.min(dp[i-1][j],dp[i][j-1])) + dp[i][j];
				}
				if(max < dp[i][j])
					max= dp[i][j];
			}
		}

		System.out.println(max * max );

	}

}