Count Good Nodes in Binary Tree

Code

# 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 preorder(node, cur_max):
            if node is None:
                return 0
            good_nodes = 0
            if node.val >= cur_max:
                good_nodes += 1
                cur_max = node.val
            good_nodes += preorder(node.left, cur_max)
            good_nodes += preorder(node.right, cur_max)
            return good_nodes
 
        return preorder(root, root.val)

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References

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