# 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 isUnivalTree(self, root):
        """
        :type root: TreeNode
        :rtype: bool
        """
        myset = set()

        def traverse(root):
            if (root == None):
                return
            myset.add(root.val)
            traverse(root.left)
            traverse(root.right)

        traverse(root)

        return True if len(myset) == 1 else False

'''
Runtime: 20 ms, faster than 54.84% of Python online submissions for Univalued Binary Tree.
Memory Usage: 11.8 MB, less than 76.47% of Python online submissions for Univalued Binary Tree.
'''