LeetCode Q250: Count Univalue Subtrees

Given a binary tree, count the number of uni-value subtrees.

A Uni-value subtree means all nodes of the subtree have the same value.

For example:
Given binary tree,

              5
             / \
            1   5
           / \   \
          5   5   5

return 4.

Solution:

Recursion, check if subtree is univalue tree and check if root's value is as same as children's.

Rnd3 solution: