Univalued Binary Tree

Easy

A binary tree is univalued if every node has the same value. Given the root, return true if the tree is univalued, otherwise false.

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

• 1 <= number of nodes <= 100
• 0 <= Node.val <= 99