Howdy! Here’s your coding interview test question for today.

A universal value tree (aka “unival”) is a tree where all nodes under it have the same value.

Given the root to a binary tree, count the number of unival subtrees.

For example, the following tree has 5 unival subtrees:

   0
  / \
 1   0
    / \
   1   0
  / \
 1   1

Write your answer in any programming language or pseudocode on gist and paste the link in the comments below!