isabella232 / lights-out

New programming challenge based a game from the 80s

Lights Out

This programming challenge is based on a game from my childhood called Lights Out. From Wikipedia:

The game consists of a 5 by 5 grid of lights. When the game starts, a random number or a stored pattern of these lights is switched on. Pressing any of the lights will toggle it and the adjacent lights. The goal of the puzzle is to switch all the lights off, preferably in as few button presses as possible.

For example:

We'll be using a 3x3 grid instead of 5x5. I've created a program in the project's root, board.rb. It takes two arguments:

1. An initial board state, expressed as nine ones (for on) and zeroes (for off). The first three characters represent the top row, the middle three the middle row, and the last three the last row. So for example, a board state of 010101011 would represent the following state:

    010
    101
    011
   

2. A optional series of button presses, expressed as digits 1-9, where 1 corresponds to the top left, 3 to the top right, 9 to the bottom right (like a phone).

So calls to board.rb will look something like this:

> ./board.rb 010111010
010
111
010
> ./board.rb 010111010 7
010
011
100
> ./board.rb 010111010 73
001
010
100
> ./board.rb 010111010 5
000
000
000

The challenge is to create a program in your language or languages of choice called lights_out that takes an initial board state and returns an efficient series of moves to turn all the lights off. For example:

> ./lights_out 0000000000

> ./lights_out 010111010
5
> ./lights_out 110001101
179

To start:

1. Create a directory based on the name of your implementation language (e.g. languages/C)
2. Create a simple Rakefile that has, at a minimum, a build task within your language's namespace (e.g. C:build). You should check the environment and fail fast if dependencies aren't met.
3. Create your implementation and run rake from the project root.

Example Rakefile

namespace :C do
  task :check do
    `which cc`
    raise "Please ensure that you have a valid C compiler" unless $?.success?
  end

  task :build => :check do
    path = File.dirname(__FILE__)
    `cd #{path}; make lights_out`
  end
end