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