What is the Zigzag Level Order Traversal pattern?

The Zigzag Level Order Traversal is a common coding interview pattern in Breadth First Search problems. It provides a structured approach to solving related algorithm challenges efficiently.

When should I use Zigzag Level Order Traversal?

Use the Zigzag Level Order Traversal pattern when you encounter problems matching its characteristics. Check the "When to Use" and "Clues" sections in the lesson for specific indicators.

Is Zigzag Level Order Traversal asked in FAANG interviews?

Yes, Zigzag Level Order Traversal is an essential pattern commonly tested in FAANG and top tech company technical interviews.

Breadth-First Search

Medium

Zigzag Level Order Traversal

Traverse levels in alternating order (left-to-right, then right-to-left).

15 min

Solve on LeetCode

Problem Understanding

Given the root of a binary tree, return the zigzag level order traversal of its nodes' values.

Level 0: Left -> Right
Level 1: Right -> Left
Level 2: Left -> Right
...

Algorithm Strategy

We use standard BFS with a Queue to process levels one by one.

Handling Zigzag:

Collect all values for the current level into a list.
Check Depth: If the current level depth is Odd, reverse the list before adding it to results.
Alternative: Use a Deque for the current level list, using push_front or push_back depending on depth.

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