MaximalSquare.java

public class Solution {
    public int maximalSquare(char[][] matrix) {
        if (matrix == null || matrix.length == 0
                || matrix[0].length == 0) return 0;

        int[][] dp = new int[matrix.length][matrix[0].length];
        int max = 0;
        for (int i = 0; i < matrix.length; i++) {
            dp[i][0] = Character.getNumericValue(matrix[i][0]);
            max = Math.max(max, dp[i][0]);
        }
        for (int i = 0; i < matrix[0].length; i++) {
            dp[0][i] = Character.getNumericValue(matrix[0][i]);
            max = Math.max(max, dp[0][i]);
        }


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