leetcode 221: Maximal Square

Maximal Square

Total Accepted: 1312 Total Submissions: 6388

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

[思路]

dynamic programing.  以当前点(x,y) = '1' 为右下角的最大正方形的边长f(x,y) = min( f(x-1,y), f(x,y-1), f(x-1,y-1)) + 1.

递推公式已建立, dp就自然而然了.

[CODE]

public class Solution {
    public 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