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Decode the Coding Interview in Elixir: Real-World Examples

Binary Tree Zigzag Level Order Traversal

Explore how to implement zigzag level order traversal in binary trees by modifying BFS with a deque to alternate between left-to-right and right-to-left node visiting. Understand the approach and complexity, enhancing your skills for coding interview challenges involving advanced tree traversal techniques.

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Description

Given a binary tree T, you have to find its nodes’ zigzag level order traversal. The zigzag level order traversal corresponds to traversing nodes from left to right and then right to left for the next level, alternating between.

You have to return the elements in each level in a two-dimensional array.

Let’s look at an example:

Coding exercise

Elixir
defmodule Solution do
  def zigzag_level_order(_root) do
    # Write your code here
  end
end

Solution

As per the problem statement, we need to traverse the tree in a level-by-level zigzag order. An intuitive approach for this problem would be to use Breadth-First Search (BFS). By default, BFS provides ordering from left to right within a single level.

We will need to modify BFS a little to get our desired output, a zigzagzigzag ...