[LeetCode]--221. Maximal Square

public class Solution {
public int maximalSquare(char[][] a) {
if (a == null || a.length == 0 || a[0].length ==0)  return 0;
int max = 0, m = a.length, n = a[0].length;
// dp[i,j] represents the length of the square whose lower-right is
//located at (i, j) , dp[i,j] = min{dp[i - 1][j - 1], dp[i - 1][j], dp[i][j - 1]}, if a[i][j] = 1,
// add 1
int[][] dp = new int[m + 1][n + 1];
for (int i = 1; i <= m; i++) {
for (int j = 1; j <= n; j++) {
if (a[i - 1][j - 1] == '1') {
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]);        //Think carefully about it!
}
}
}
return (int)(Math.pow(max, 2));
}
}