LeetCode - Maximum Depth of Binary Tree

Maximum Depth of Binary Tree

2014.1.7 23:26

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.

Solution:

　　depth(tree)  = max(depth(left subtree), depth(right subtree)) + 1;

　　depth(nullptr) = 0;

　　Time complexity is O(n), where n is the number of nodes in the tree. Space complexity is O(1).

Accepted code:

 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         // Note: The Solution object is instantiated only once and is reused by each test case.

14         if(root == NULL){

15             return 0;

16         }else{

17             return 1 + mymax(maxDepth(root->left), maxDepth(root->right));

18         }

19     }

20 private:

21     const int &mymax(const int &a, const int &b) {

22         return (a > b ? a : b);

23     }

24 };