2025-08-01 16:30:30 +0000 UTC

# 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:
        def dfs(node: Optional[TreeNode]) -> bool:
            if node is None:
                return True
            if node.left and node.val != node.left.val:
                return False
            if node.right and node.val != node.right.val:
                return False
            return dfs(node.left) and dfs(node.right)
        return dfs(root)