Maximal Square

Given a 2D binary matrix filled with 0’s and 1’s, find the largest square containing only 1’s and return its area.

For example, given the following matrix:

1 0 1 0 0
1 0 1 1 1
1 1 1 1 1
1 0 0 1 0

Return 4.

Solution:

public class Solution {
    public int maximalSquare(char[][] matrix) {
        if(matrix.length==0) return 0;
        int[][] dp = new int[matrix.length+1][matrix[0].length+1];
        int max = 0;
        for(int i=1; i<=matrix.length; i++){
            for(int j=1; j<=matrix[0].length; j++){
                if(matrix[i-1][j-1]=='0'){
                    dp[i][j] = 0;
                } else {
                    dp[i][j] = Math.min(dp[i-1][j-1], Math.min(dp[i-1][j], dp[i][j-1])) + 1;
                    max = Math.max(max, dp[i][j]*dp[i][j]);
                }
            }
        }
        return max;
    }
}