直接对二叉树进行后序遍历即可
import java.util.*;
/*
* public class TreeNode {
* int val = 0;
* TreeNode left = null;
* TreeNode right = null;
* }
*/
public class Solution {
/**
*
* @param root TreeNode类
* @return int整型
*/
public int maxDepth (TreeNode root) {
// write code here
if(root == null){
return 0;
}
int left = maxDepth(root.left);
int right = maxDepth(root.right);
return Math.max(left,right)+1;
}
}