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Decode the Coding Interview in Elixir: Real-World Examples

Spiral Matrix

Explore how to return all elements of a matrix in clockwise spiral order. Understand the layer-by-layer approach and practice solving this common coding interview problem using Elixir. This lesson helps you develop skills to analyze matrix traversal and optimize your solution's time and space complexity.

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Description

Given an m * n matrix, you have to return all the matrix elements in spiral order. The spiral order signifies traversing the matrix in clockwise order.

Let’s review the spiral order below:

Coding exercise

Elixir
defmodule Solution do
  def spiral_order(_matrix) do
    # Write your code here
  end
end

Solution

To solve this problem, we will use a layer by layer approach. In this approach, we iterate over the outer layers’ elements in clockwise order, followed by the inner layer’s elements.

For each layer, we will start from the top left corner and iterate over the elements in that layer. We define the top-left coordinates, say (r1, c1) and bottom-right coordinates, say (r2, c2).

As we explore the layers in clockwise order, we have to:

  1. Iterate the top row, (r1, c), where c ranges from c1 to c2.

  2. Iterate the right side, (r, c2), where r ranges from r1 + 1 to r2.

  3. Iterate the bottom row, (r2, c) ...