103. Binary Tree Zigzag Level Order Traversal

https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/

Python

DFS

from collections import deque


class Solution:
    def zigzagLevelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
        if not root:
            return []

        result = []

        def dfs(node, level):
            if level >= len(result):
                result.append(deque([node.val]))
            else:
                if level % 2 == 0:
                    result[level].append(node.val)
                else:
                    result[level].appendleft(node.val)

            if node.left:
                dfs(node.left, level+1)

            if node.right:
                dfs(node.right, level+1)

        dfs(root, 0)
        return result

BFS

(TODO)