Maximum Depth of Binary Tree 二叉树的深度

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.

此题是经典的求二叉树深度深度题目，可采用递归的方式，以此求每个节点的左子树深度和右子树深度，然后返回该节点左右子树深度最大的那个即为该节点的深度

具体代码如下：

 /**
  * 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 ;

         int nleft = maxDepth(root->left);
         int nright = maxDepth(root->right);

         return (nleft > nright) ? (nleft+) : (nright+);
     }
 };