trainworks

Trainworks 🚂

Problem Definition

The local commuter railroad services a number of towns in Kiwiland. Because of monetary concerns, all of the tracks are 'one-way.' That is, a route from Kaitaia to Invercargill does not imply the existence of a route from Invercargill to Kaitaia. In fact, even if both of these routes do happen to exist, they are distinct and are not necessarily the same distance!

The purpose of this problem is to help the railroad provide its customers with information about the routes. In particular, you will compute the distance along a certain route, the number of different routes between two towns, and the shortest route between two towns.

Input

A directed graph where a node represents a town and an edge represents a route between two towns. The weighting of the edge represents the distance between the two towns. A given route will never appear more than once, and for a given route, the starting and ending town will not be the same town.

Output

For test input 1 through 5, if no such route exists, output 'NO SUCH ROUTE'. Otherwise, follow the route as given; do not make any extra stops! For example, the first problem means to start at city A, then travel directly to city B (a distance of 5), then directly to city C (a distance of 4).

1. The distance of the route A-B-C.
2. The distance of the route A-D.
3. The distance of the route A-D-C.
4. The distance of the route A-E-B-C-D.
5. The distance of the route A-E-D.
6. The number of trips starting at C and ending at C with a maximum of 3 stops. In the sample data below, there are two such trips: C-D-C (2 stops). and C-E-B-C (3 stops).
7. The number of trips starting at A and ending at C with exactly 4 stops. In the sample data below, there are three such trips: A to C (via B,C,D); A to C (via D,C,D); and A to C (via D,E,B).
8. The length of the shortest route (in terms of distance to travel) from A to C.
9. The length of the shortest route (in terms of distance to travel) from B to B.
10. The number of different routes from C to C with a distance of less than 30. In the sample data, the trips are: CDC, CEBC, CEBCDC, CDCEBC, CDEBC, CEBCEBC, CEBCEBCEBC.

Test Input

For the test input, the towns are named using the first few letters of the alphabet from A to E. A route between two towns (A to B) with a distance of 5 is represented as AB5.

Graph: AB5, BC4, CD8, DC8, DE6, AD5, CE2, EB3, AE7

Expected Output:

Output #1: 9
Output #2: 5
Output #3: 13
Output #4: 22
Output #5: NO SUCH ROUTE
Output #6: 2
Output #7: 3
Output #8: 9
Output #9: 9
Output #10: 7

Installation

Note: Since the project is not yet publicly available, there's no way to fork/clone/install it from Rubygems. The only way to use the gem is getting its source code and running rake install. It will install the local gem so you'll be able to require it in irb for example.

First you'll need Bundler in order to install the dependencies (which are only necessary for development).

$ gem install bundler

Add this line to your application's Gemfile:

gem 'trainworks'

And then execute:

$ bundle

Or install it yourself as:

$ gem install trainworks

Usage

require 'trainworks'

railroad = Trainworks::Railroad.new('examples/input.txt')

# assuming you have the following graph
# AB5, BC4, CD8, DC8, DE6, AD5, CE2, EB3, AE7
railroad.distance("A-B-C")
# => 9.0

railroad.distance("A-Z")
# => "NO SUCH ROUTE"

railroad.shortest_distance(from: "A", to: "C")
# => 9.0

railroad.trips(from: "C", to: "C", with_max_stops: 3)
# => [["C","D","C"], ["C","E","B","C"]]

railroad.trips(from: "A", to: "C", with_exact_stops: 4)
# => [["A", "B", "C", "D", "C"], ["A", "D", "C", "D", "C"], ["A", "D", "E", "B", "C"]]

railroad.trips(from: "C", to: "C", with_max_distance: 30)
# => [["C","D","C"], ["C","E","B","C"], ["C","E","B","C","D","C"], ["C","D","C","E","B","C"], ["C","D","E","B","C"], ["C","E","B","C","E","B","C"], ["C","E","B","C","E","B","C","E","B","C"]]

Development & Contribution

Note: This section is only valid after the project is publicly available.

1. Fork this repository.
2. Clone it into your machine and run bundle install.
3. Add your changes.
4. Make sure the specs are green by running rspec.
5. Make sure the code style is respected by running rubocop.
6. Open a pull request.

License

The gem is available as open source under the terms of the MIT License.