Univalued Binary Tree

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:

# 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:
        l = True
        r = True
        if root:
            if root.left and (root.val != root.left.val or not self.isUnivalTree(root.left)):
                l = False
            if root.right and (root.val != root.right.val or not self.isUnivalTree(root.right)):
                r = False
        return l and r