#103

Binary Tree Zigzag Level Order Traversal

medium · verified · 63.3% accepted · 11,990 likes · top 66%

tree · breadth-first search · binary tree

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Description

Given the root of a binary tree, return the zigzag level order traversal of its nodes' values. (i.e., from left to right, then right to left for the next level and alternate between).

Example 1:

Input: root = [3,9,20,null,null,15,7]
Output: [[3],[20,9],[15,7]]

Example 2:

Input: root = [1]
Output: [[1]]

Example 3:

Input: root = []
Output: []

Solution