题目如下：

A binary tree is univalued if every node in the tree has the same value.

Return true if and only if the given tree is univalued.

 

Example 1:

Input: [1,1,1,1,1,null,1]Output: true

Example 2:

Input: [2,2,2,5,2]Output: false

 

Note:

1. The number of nodes in the given tree will be in the range [1, 100].
2. Each node's value will be an integer in the range [0, 99].

解题思路：送分题。

代码如下：

# Definition for a binary tree node.# class TreeNode(object):#     def __init__(self, x):#         self.val = x#         self.left = None#         self.right = Noneclass Solution(object):    def recursive(self,node,v):        if node.val != v:            return False        r1 = r2 = True        if node.left != None:            r1 = self.recursive(node.left,v)        if node.right != None:            r2 = self.recursive(node.right,v)        return r1 and r2    def isUnivalTree(self, root):        """        :type root: TreeNode        :rtype: bool        """        if root == None:            return True        return self.recursive(root,root.val)