1457. Pseudo-Palindromic Paths in a Binary Tree

https://leetcode.com/problems/pseudo-palindromic-paths-in-a-binary-tree/

Python

DFS

class Solution:
    def pseudoPalindromicPaths (self, root: Optional[TreeNode]) -> int:
        def dfs(node, path_origin: set):
            if not node:
                return 0
            
            path = path_origin.copy()
            if node.val in path:
                path.remove(node.val)
            else:
                path.add(node.val)

            if not node.left and not node.right:
                # Current node is leave, check the path
                return 1 if len(path) <= 1 else 0
            
            return dfs(node.left, path) + dfs(node.right, path)
        
        return dfs(root, set())