Description
https://leetcode.com/problems/univalued-binary-tree/
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].
Explanation
Traverse each note and see if the value is unique across the tree.
Python Solution
# 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: TreeNode) -> bool:
if not root:
return True
self.unique_value = root.val
return self.helper(root)
def helper(self, root):
if not root:
return True
if root.val != self.unique_value:
return False
return self.helper(root.left) and self.helper(root.right)- Time Complexity: O(N))
- Space Complexity: O(1)