1448. Count Good Nodes in Binary Tree

https://leetcode.com/problems/count-good-nodes-in-binary-tree/

Python

from math import inf


class Solution:
    def goodNodes(self, root: TreeNode) -> int:

        def dfs(node: TreeNode, max_val: int):
            if not node:
                return 0

            count = 1 if node.val >= max_val else 0

            count += dfs(node.left, max(max_val, node.val))
            count += dfs(node.right, max(max_val, node.val))
            return count

        return dfs(root, -inf)