leetcode#144 Binary Tree Preorder Traversal

1. 문제

• https://leetcode.com/problems/binary-tree-preorder-traversal/

2. 나의 풀이

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    def foo(self, node, result):
        if node:
            result.append(node.val)
            
            if node.left:
                self.foo(node.left, result)
            if node.right:
                self.foo(node.right, result)
            return result
        
    
    def preorderTraversal(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """

        return self.foo(root, [])

3. 남의 풀이