965. Univalued Binary Tree-单值二叉树

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:

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

Solution:

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

class Solution:
    def isUnivalTree(self, root: TreeNode) -> bool:
        sin_va = root.val
        def traverse(root, value):
            if root == None:
                return True
            else:
                if root.val != value:
                    return False
                elif root.val == value:
                    left = traverse(root.left, value)
                    right = traverse(root.right, value)
                    return left and right
        return traverse(root, root.val)