[QUIZ] Sliding Puzzle (#196)

Discussion in 'Ruby' started by Daniel Moore, Mar 13, 2009.

  1. Daniel Moore

    Daniel Moore Guest


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    ## Sliding Puzzle (#196)

    Bienvenidos fellow Rubyists,

    This weeks quiz will be to create and implement a [sliding puzzle][1].
    The puzzle must be playable from keyboard input. The program will
    generate a puzzle in a random configuration and the puzzle generated
    must be solvable. You may create either the 8-puzzle or the 15-puzzle.
    You may include a mode that will automatically solve the puzzle or
    present a hint.

    The puzzle must throw a small party when solved.

    Bonus: Have the puzzle be displayed as an ascii art image that needs
    to be arranged instead of simple numbers.

    [1]: http://en.wikipedia.org/wiki/Fifteen_puzzle

    Have Fun!
    Daniel Moore, Mar 13, 2009
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  2. Daniel Moore

    Daniel Moore Guest

    [SUMMARY] Sliding Puzzle (#196)

    The sole submission to this week's quiz comes from Martin Boese.
    Martin provided a simple and versatile solution. It can generate
    puzzles of any size, and is able to shuffle to a random starting
    configuration. It also throws a nice party when the player succeeds.

    The program provides a driver that reads keyboard commands and
    translates them into the correct actions on the puzzle class. The
    program accepts four movement commands as well as commands to quit and

    Here's a look at the puzzle's shuffle method to randomize the configuration:

    def shuffle
    100.times { move 'udlr'[(rand*4).to_i].chr }

    The shuffling is done by making 100 random moves, this ensures that
    the puzzle remains solvable; a random shuffling of the tiles without
    maintaining the movement constraints is not necessarily solvable.
    Additionally, this leverages the existing functionality of the `move`
    method to keep the code simple. One potential drawback is that this
    doesn't select all possible starting positions with equal probability.
    However, having the random configurations generated with equal
    probability wasn't a quiz requirement, and it is often best to go with
    the least complex solution that meets the requirements.

    The method to detect whether or not the puzzle is solved also
    leverages existing functionality to reduce complexity, it checks if
    the current board is equal to a newly created board. Because the newly
    created board starts in the solved position and the board is an array
    of integers, this leads to a short and sweet definition:

    def solved?
    @board == mkboard(@x,@y) && @moved

    The check for `@moved` to be true is to prevent the puzzle from
    partying when the game is first created and before it is shuffled.
    Speaking of the party, here's the section responsible for that magical

    10.times { $stdout.print '*'; sleep 0.1; $stdout.flush }
    puts " You won!\n"

    It creates a rapid display of asterisks and congratulates the player!

    Thank you, Martin, for a wonderful solution!


    - Daniel
    Daniel Moore, Mar 23, 2009
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