Maximal Square，Given a 2D binary matrix filled with 0's and 1's, find the largest squar

Maximal Square

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

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 笔记
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.

public class Solution {  
	
	public static void main(String[] args) {
		char[][]  array={{'1','0','0'},{'1','1','1'},
				{'1','1','1'}};
		System.out.println(maximalSquare(array));
	}
	 public static int maximalSquare(char[][] matrix) {  
	        if(matrix==null || matrix.length==0 || matrix[0].length==0) return 0;  
	          
	        int n = matrix.length;  
	        int m = matrix[0].length;  
	          
	        int[][] d = new int[n][m];  
	        int max = 0;  
	  
	        for(int i=0; i<n; i++) {  
	            if(matrix[i][0]=='1') {  
	                d[i][0] = 1;  
	                max = 1;  
	            }  
	        }  
	          
	        for(int j=0; j<m; j++) {  
	            if(matrix[0][j]=='1') {  
	                d[0][j] = 1;  
	                max = 1;  
	            }  
	        }  
	        for(int i=1; i<n; i++) {  
	            for(int j=1; j<m; j++) {  
	                if(matrix[i][j]=='0') d[i][j]=0;  
	                else {  
	                    d[i][j] = Math.min( Math.min( d[i-1][j], d[i][j-1]), d[i-1][j-1] ) + 1; /////去上方，左方，左上方的最小值，再加1
	                    max = Math.max(max, d[i][j]);     //////算法真的很精辟
	                }  
	            }  
	        }  
	        return max*max;  
	    }  
}  

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