【leetnode刷题笔记】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.

解题：

递归就行：根节点为空，返回0；一个子树根节点为空，另一个子树根节点不为空，就返回根节点不为空的子树高度；否则返回两个子树中高度大者加一。

代码：

 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)

14             return 0;

15         if(root->left != NULL && root->right == NULL)

16             return maxDepth(root->left)+1;

17         if(root->right != NULL && root->left == NULL)

18             return maxDepth(root->right)+1;

19         int h_left = maxDepth(root->left);

20         int h_right = maxDepth(root->right);

21         return h_left > h_right ? h_left+1:h_right+1;

22     }

23 };

 Java版本代码：

 1 /**

 2  * Definition for binary tree

 3  * public class TreeNode {

 4  *     int val;

 5  *     TreeNode left;

 6  *     TreeNode right;

 7  *     TreeNode(int x) { val = x; }

 8  * }

 9  */

10 public class Solution {

11     public int maxDepth(TreeNode root) {

12         return maxDepthHelper(root, 0);

13     }

14     int maxDepthHelper(TreeNode root,int height){

15         if(root == null)

16             return height;

17         int l = maxDepthHelper(root.left, height+1);

18         int r = maxDepthHelper(root.right, height+1);

19         return l > r?l:r;

20     }

21 }