jobsorter

Install

Clone the repo:

git clone https://github.com/tomdracz/jobsorter.git

Run bundle install from the project folder to install rspec:

bundle install

Running script

Load the library

require './lib/jobs_sorter.rb'

Initialize new JobsSorter object passing jobs string

jobs_sorter = JobsSorter.new("jobs_string_here")

Run the sort method to see an array of ordered jobs

jobs_sorter.sort

Running tests

From the project directory:

rspec

Notes on the implementation

The problem presented below can be considered an example of topological sorting, hence the existing TSort Ruby standard lib has been used by opening the Hash class to implement tsort there. Using TSort lib is a quick and easy solution and offers things like detecting cyclic dependecies out of the box

Description of the problem

Imagine we have a list of jobs, each represented by a character. Because certain jobs must be done before others, a job may have a dependency on another job. For example, a may depend on b, meaning the final sequence of jobs should place b before a. If a has no dependency, the position of a in the final sequence does not matter.

Given you’re passed an empty string (no jobs), the result should be an empty sequence.
Given the following job structure:

a =>

The result should be a sequence consisting of a single job a.
Given the following job structure:

a =>

b =>

c =>

The result should be a sequence containing all three jobs abc in no significant order.
Given the following job structure:

a =>

b => c

c =>

The result should be a sequence that positions c before b, containing all three jobs abc.
Given the following job structure:

a =>

b => c

c => f

d => a

e => b

f =>

The result should be a sequence that positions f before c, c before b, b before e and a before d containing all six jobs abcdef.
Given the following job structure:

a =>

b =>

c => c

The result should be an error stating that jobs can’t depend on themselves.
Given the following job structure:

a =>

b => c

c => f

d => a

e =>

f => b

The result should be an error stating that jobs can’t have circular dependencies.

tomdracz / jobsorter