题目地址(221. 最大正方形)

Posted 2022-04-29 潜行前行

题目地址(221. 最大正方形)

https://leetcode-cn.com/problems/maximal-square/

题目描述

在一个由 '0' 和 '1' 组成的二维矩阵内，找到只包含 '1' 的最大正方形，并返回其面积。

 

示例 1：

输入：matrix = [["1","0","1","0","0"],["1","0","1","1","1"],["1","1","1","1","1"],["1","0","0","1","0"]]
输出：4


示例 2：

输入：matrix = [["0","1"],["1","0"]]
输出：1


示例 3：

输入：matrix = [["0"]]
输出：0


 

提示：

m == matrix.length
n == matrix[i].length
1 <= m, n <= 300
matrix[i][j] 为 '0' 或 '1'

关键点

• 依赖 dp[i-1][j-1] 的最大正方形 数

代码

• 语言支持：Java

Java Code:

class Solution 
    public int maximalSquare(char[][] matrix) 
        int[][] dp = new int[matrix.length][matrix[0].length];
        int res = 0;
        for(int i=0;i<matrix.length;i++)
            for(int j=0;j<matrix[0].length;j++)
                if(i == 0 || j==0 || dp[i-1][j-1] == 0 || matrix[i][j] == '0' )
                    dp[i][j] = matrix[i][j] - '0';
                else
                    dp[i][j] = 1;
                    int n = dp[i-1][j-1];
                    for(int k = 1; k<=n; k++)
                        if(matrix[i-k][j] == '1' && matrix[i][j-k] == '1')
                            dp[i][j] += 1 ;
                        else
                            break;
                        
                    
                
                res = Math.max(res,dp[i][j]);
            
        
        return res * res;
    

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