最大正方形

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：

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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

代码

9%98%

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class Solution {
    public int maximalSquare(char[][] matrix) {
        if(matrix==null||matrix.length==0)return 0;
        int[][] m=new int[matrix.length][matrix[0].length];
        int max=0;
        for(int i=0;i<matrix.length;i++)
        {
            for(int j=0;j<matrix[i].length;j++)
            {
                if(matrix[i][j]=='0'){
                    m[i][j]=0;
                    continue;
                }
                int lu=     (i!=0&&j!=0) ? m[i-1][j-1]:0;
                int left=   (j!=0)       ? m[i][j-1]:0;
                int up=     (i!=0)       ? m[i-1][j]:0;

                m[i][j]=(Math.min(lu,Math.min(left,up))+1)*(matrix[i][j]-'0');
                if(m[i][j]>max)max=m[i][j];

            }
        }
        return max*max;
    }
}