題目如下：

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].

解題思路：送分題。

程式碼如下：

# 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 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)