【leetcode】Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

利用递归。

也可以使用栈和队列，即使用DFS和BFS方法。

C++：

 1 /**
 2  * Definition for binary tree
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     int maxDepth(TreeNode *root) {
13         if(root==NULL) return 0;
14         if(root&&root->left==NULL&&root->right==NULL) return 1;
15         int i=1;
16         int j=1;
17         i=maxDepth(root->left);
18         j=maxDepth(root->right);
19
20         if(i>j)
21             return i+1;
22         else
23             return j+1;
24     }
25 };

python:

1 class Solution:
2     # @param root, a tree node
3     # @return an integer
4     def maxDepth(self, root):
5         if root is None:
6             return 0
7         else:
8             return max(self.maxDepth(root.left),self.maxDepth(root.right))+1

递归的思想很重要。