*LeetCode 221 最大正方形（中等）

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：

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

思路与代码

动态规划

dp[i][j]表示以 (i,j)(为右下角，且只包含 '1' 的正方形的边长最大值。

核心是dp(i,j)=min(dp(i−1,j),dp(i−1,j−1),dp(i,j−1))+1

证明过程来自LeetCode

class Solution {
   
    public int maximalSquare(char