Understanding Weird Binary Search Behavior in Ruby

Explore the common pitfalls of recursive binary search in Ruby, and how to implement a reliable solution step-by-step.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Weird binary search behavior in Ruby

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding Weird Binary Search Behavior in Ruby

Binary search is a classic algorithm used to efficiently find elements within a sorted array. However, even seasoned developers can encounter unexpected behavior while implementing this algorithm, especially in a language like Ruby. In this post, we’ll delve into a common issue in binary search code, highlight what went wrong, and walk through a corrected implementation.

The Problem

A user recently posed a question regarding their implementation of a recursive binary search in Ruby. They faced a peculiar problem: the binary search function would return unexpected results unless specific keys like 21 or 3 were queried. With other keys, it returned odd indices or even -1, leading to considerable confusion.

The Original Implementation

Here’s the initial code shared by the user:

[[See Video to Reveal this Text or Code Snippet]]

What Went Wrong?

The issue with the original code lies in how the recursive function manipulated the array:

Array Slicing: When the search moves left or right, the original code was slicing the array. This means that the search was not working with the original indices anymore but rather with a new, smaller array.

For example:

[[See Video to Reveal this Text or Code Snippet]]

This line creates a new array, starting from low and going up to mid - 1. As a result, when it finally found a match, it returned 0 as the index of this new array instead of the original array.

Incorrect Base Working Indices: The method used to set the base case and calculate mid also seemed misleading.

The Solution

Here’s a corrected and more effective version of the binary search algorithm which maintains the integrity of the original array and correctly uses the indices passed to the function:

[[See Video to Reveal this Text or Code Snippet]]

Key Changes Made:

Passing low and high: We’re now passing low and high indices to the function directly, without altering or slicing the original array.

Default Parameter for high: The high parameter now defaults to nil, which allows us to set it based on the array’s length only once at the beginning.

Utilization of Case Statement: Using the spaceship operator <=>, we efficiently determine which direction to proceed in the search.

Conclusion

The adjustments made to the binary search implementation in Ruby aim to address the issues observed in the original code. With a clearer structure and proper handling of the original array, this solution is now efficient and reliable. It's crucial to understand how array slicing can significantly disrupt index tracking in recursive algorithms. Feel free to test this implementation with any sorted array and different keys!

With these adjustments, we hope you can implement your binary search in Ruby without the weird behavior, paving the way for more complex algorithms in your coding journey.