Title: Enter a binary tree, find the depth of the tree. Forming a path tree from the root node to the leaf node sequentially passes (including the root, leaf nodes), the depth of the length of the longest path in the tree.

Ideas: recursion.

```
/*
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};*/
class Solution {
public:
int TreeDepth(TreeNode* pRoot)
{
if(pRoot==nullptr) return 0;
return max(TreeDepth(pRoot->left)+1,TreeDepth(pRoot->right)+1);
}
};
```

python:

```
# -*- coding:utf-8 -*-
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def TreeDepth(self, pRoot):
# write code here
if(pRoot==None):
return 0
left = self.TreeDepth(pRoot.left)
right=self.TreeDepth(pRoot.right)
if left >right:
return left+1
else:
return right+1
```