Maximum Depth of Binary Tree

　　　　这道题为简单题

　　题目：

　　　　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.

　　思路：

　　　　我是用递归做的，当然也可以用深搜和广搜，递归的话就是比较左右子树的深度然后返回

　　代码：

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def maxDepth(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        if not root: return 0
        
        left = self.maxDepth(root.left)
        right = self.maxDepth(root.right)
        if left > right:
            return 1 + left
        else:
            return 1 + right