250. Count Univalue Subtrees

https://leetcode.com/problems/count-univalue-subtrees

Python

class Solution:
    def __init__(self):
        self.ans = 0

    def countUnivalSubtrees(self, root: Optional[TreeNode]) -> int:
        if not root:
            return 0

        if self.check_tree(root, root.val):
            self.ans += 1

        self.countUnivalSubtrees(root.left)
        self.countUnivalSubtrees(root.right)

        return self.ans

    def check_tree(self, node: Optional[TreeNode], parent_var: int) -> int:
        if not node:
            return True

        if  node.val == parent_var \
        and self.check_tree(node.left, parent_var) \
        and self.check_tree(node.right, parent_var):
            return True

        return False