Binary Tree Zigzag Level Order Traversal

leetcode/binary-tree-zigzag-level-order-traversal

Code

• O(N) : 28 ms, faster than 82.86% of Python3 online submissions

class Solution:
    def zigzagLevelOrder(self, root: TreeNode) -> List[List[int]]:
        if not root:
            return []
        depth = 0
        queue = [root]
        answer = []
        reverse = False
        while queue:
            if reverse:
                answer.append([n.val for n in queue[::-1]])
            else:
                answer.append([n.val for n in queue])
            nextQueue = []
            for node in queue:
                if node.left:
                    nextQueue.append(node.left)
                if node.right:
                    nextQueue.append(node.right)
            queue = nextQueue
            reverse = False if reverse else True
        return answer