1448-count-good-nodes-in-binary-tree.py

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def goodNodes(self, root: TreeNode) -> int:
        def dfs(node, maxVal):
            if not node:
                return 0
            newMax = max(node.val, maxVal)
            plus = 1 if newMax == node.val else 0
            return plus + dfs(node.left, newMax) + dfs(node.right, newMax)
            
        return dfs(root, root.val)