How to do quick sort in Elixir

Key takeaways:
Quick sort is a divide-and-conquer sorting algorithm known for its high efficiency and performance.
Quick sort in Elixir shows the strengths of functional programming by allowing concise and readable solutions.
Quick sort divides arrays into smaller subarrays around a pivot and recursively sorts them to achieve the final sorted array.
The quick sort implementation in Elixir is simple and adaptable, making it easy for developers to understand and modify based on their needs.
Learning quick sort in Elixir enhances programming skills and strengthens problem-solving abilities in functional programming.

Sorting is a pivotal operation in computer science, and the choice of a sorting algorithm can significantly impact performance. One such algorithm known for its efficiency is quick sort. In this Answer, we’ll look at the implementation of quick sort in Elixir, a functional programming language that operates on the Erlang virtual machine.

Understanding quick sort

Quick sort is a divide-and-conquer algorithm that efficiently sorts elements in a given array. The algorithm chooses a "pivot" element and divides the rest of the elements into two subarrays: one containing elements less than the pivot and the other containing the greater ones. The same process is repeated recursively on the subarrays until the entire array is sorted.

Demonstration

The following illustration shows how the quick sort algorithm works:

defmodule QuickSort do
  # Base case: An empty list is already sorted
  def sort([]), do: []
  # Recursive case: Sort smaller and greater subarrays
  def sort([pivot | remaining]) do
    # Partition the array into smaller and greater subarrays
    {smaller, greater} =
      Enum.reduce(remaining, {[], []}, fn item, {smaller_acc, greater_acc} ->
        if item <= pivot, do: {[item | smaller_acc], greater_acc}, else: {smaller_acc, [item | greater_acc]}
      end)
    # Combine sorted subarrays and pivot
    sort(smaller) ++ [pivot] ++ sort(greater)
  end
end
# Example usage
test_list = [5, 8, 7, 9, 1, 0, 4]
sorted_list = QuickSort.sort(test_list)
IO.inspect(sorted_list) # [0, 1, 4, 5, 7, 8, 9]

Explanation

In the code above:

Line 1: We define a module named QuickSort.
Line 2: We define the sort/1 function that serves as our entry point. If the input list is empty, this function will return an empty list.
Lines 3–7: For a non-empty list, the first element is chosen as the pivot, and the remaining elements are partitioned into two lists: smaller (elements less than or equal to pivot) and greater (elements greater than pivot) using the Enum.reduce/3 method.
Line 9: The sort/1 function is then applied recursively to both subarrays, and the results are combined to achieve the final sorted array.
Lines 14–16: We create an input list to test our implementation and print the result.

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Conclusion

Quick sort stands out as a reliable sorting algorithm, and implementing it in Elixir showcases the elegance and conciseness that functional programming languages offer. The simplicity of the Elixir code, coupled with the efficiency of quick sort, provides a compelling solution for sorting arrays with high performance. Understanding and implementing such algorithms enrich our grasp of fundamental computer science principles and enhance our ability to solve complex problems.

Frequently asked questions

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What is quick sort in Elixir?

Quick sort in Elixir is a functional implementation of the quick sort algorithm, a divide-and-conquer approach for sorting elements.

How does quick sort work in Elixir?

Quick sort in Elixir selects a pivot, partitions the elements into smaller and greater subarrays, and recursively sorts these subarrays.

Why is quick sort efficient?

Quick sort is efficient because it reduces the problem size significantly at each step using partitioning, achieving an average time complexity of $O(n log n)$ .

Is quick sort stable or unstable?

Quick sort is generally considered unstable because it may not preserve the relative order of equal elements.

Can quick sort handle large datasets in Elixir?

Yes, quick sort is efficient for large datasets, and Elixir’s functional paradigm ensures clean and concise code for implementation.

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