【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：

 /**
  * Definition for binary tree
  * struct TreeNode {
  *     int val;
  *     TreeNode *left;
  *     TreeNode *right;
  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
  * };
  */
 class Solution {
 public:
     int maxDepth(TreeNode *root) {
         if(root == NULL)
             return ;
         if(root->left != NULL && root->right == NULL)
             return maxDepth(root->left)+;
         if(root->right != NULL && root->left == NULL)
             return maxDepth(root->right)+;
         int h_left = maxDepth(root->left);
         int h_right = maxDepth(root->right);
         return h_left > h_right ? h_left+:h_right+;
     }
 };

Java版本代码：

 /**
  * Definition for binary tree
  * public class TreeNode {
  *     int val;
  *     TreeNode left;
  *     TreeNode right;
  *     TreeNode(int x) { val = x; }
  * }
  */
 public class Solution {
     public int maxDepth(TreeNode root) {
         return maxDepthHelper(root, 0);
     }
     int maxDepthHelper(TreeNode root,int height){
         if(root == null)
             return height;
         int l = maxDepthHelper(root.left, height+1);
         int r = maxDepthHelper(root.right, height+1);
         return l > r?l:r;
     }
 }