aloalgoBinary Tree Zigzag Level Order Traversal
Medium
You are given the root of a binary tree.
Your task is to return the zigzag level order traversal of its nodes' values.
Note that:
- The traversal should alternate direction for each level: left to right for the first level, right to left for the second, left to right for the third, and so on.
Return the zigzag level order traversal as a list of lists of integers, where each inner list represents a level's values.
Example 1
Input
Output
[ [3], [20, 9], [15, 7] ]
Explanation:
Level 0: [3] (left to right). Level 1: [20,9] (right to left). Level 2: [15,7] (left to right).
Example 2
Input
Output
[ [1] ]
Explanation:
Only one node at level 0 (left to right).
Example 3
Input
None
Output
[ ]
Explanation:
The tree is empty, so no nodes to traverse.
Example 4
Input
Output
[ [1], [3, 2], [4, 5] ]
Explanation:
Level 0: [1] (left to right). Level 1: [3,2] (right to left). Level 2: [4,5] (left to right).
Input
Output
[ [3], [20, 9], [15, 7] ]