965. Univalued Binary Tree

Problem Link

Description

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A binary tree is uni-valued if every node in the tree has the same value.

Given the root of a binary tree, return true if the given tree is uni-valued, or false otherwise.

 

Example 1:

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

Example 2:

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

 

Constraints:

• The number of nodes in the tree is in the range [1, 100].
• 0 <= Node.val < 100

Solution

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Python3

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def isUnivalTree(self, root: Optional[TreeNode]) -> bool:
        value = root.val
        
        def go(node):
            if not node: return True
            
            if node.val != value: return False
            
            return go(node.left) and go(node.right)
        
        return go(root)