Maximal Square Leetcode


#1

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

Example:

Input: 

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

Output: 4

#2

The below code uses dynamic programming to bottom up build the max size of any square.

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