jonnagel / bowling_drop

A fun interview question

Introduction

Recently during an interview I was asked how I would approach a problem. At face value the question could be seen as a binary search optimization problem but the intent was to determine how I would interact with questioner.

The question as phrased: "Given 2 bowling balls that need drop hardness testing, efficiently determine their breaking floor"

• When a ball is dropped at or above breaking floor it will break.
• There are only 2 balls.
• Minimise test drops.

The answer to the basic question of how to check with the fewest steps and limited to 2 balls is 10.

TL;DR Check every 10 floors until a break

In English - Start at the tenth floor going up by 10 floors for each unbroken ball, leaving one ball in reserve yields an average of 12.36 checks.

The background can be found in here

Note: The problem I was given is slightly different than the one described in background.md