力扣-221-最大正方形

package LeetCode;

public class LeetCode221_2 {
    public static int maximalSquare(char[][] matrix) {
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) return 0;
        
        int n = matrix.length, m = matrix[0].length;
        int ans = -1;
        
        int[][] dp = new int[n][m];
        
        for(int i = 0; i < n; i++) {
            if(matrix[i][0] == '1') dp[i][0] = 1;
        }
        
        for(int j = 0; j < m; j++) {
            if(matrix[0][j] == '1') dp[0][j] = 1;
        }
        
        for(int i = 1; i < n; i++) {
            for(int j = 1; j < m; j++) {
                if(matrix[i][j] == '1') 
                    dp[i][j] = Math.min(dp[i-1][j-1], Math.min(dp[i][j-1], dp[i-1][j])) + 1;
            }
        }
        
        for(int i = 0; i < n; i++) {
             for(int j = 0; j < m; j++) {
                 ans = Math.max(ans, dp[i][j]);
            }  
        }
        return ans * ans;
    }
    
    public static void main(String[] args) {
        char[][] matrix = {{'1','0','1','0','0'},
                    {'1','0','1','1','1'},
                    {'1','1','1','1','1'},
                    {'1','0','0','1','0'}};
        int res = maximalSquare(matrix);
        System.out.println(res);
    }
}