rock_paper_scissors.md

Back to main README

Rock-Paper-Scissors

Specs: spec/rock_paper_scissors_spec.rb

Skeleton: lib/rock_paper_scissors.rb

In a game of rock-paper-scissors, each player chooses to play Rock (R), Paper (P), or Scissors (S). The rules are: Rock breaks Scissors, Scissors cuts Paper, but Paper covers Rock.

In a round of rock-paper-scissors, each player's name and strategy is encoded as an array of two elements

    [ "Armando", "P" ]  # => Armando plays Paper
    [ "Dave", "S" ]     # => Dave plays Scissors

(In this example, Dave would win because Scissors cuts Paper.)

A. Game Winner

Create a RockPaperScissors class with a class method winner that takes two 2-element arrays like those above, and returns the one representing the winner:

    RockPaperScissors.winner(['Armando','P'], ['Dave','S'])
       # => ['Dave','S']

If either player's strategy is something other than "R", "P" or "S" (case-SENSITIVE), the method should raise a RockPaperScissors::NoSuchStrategyError exception and provide the message: "Strategy must be one of R,P,S".

If both players use the same strategy, the first player is the winner.

B. Tournament

A rock-paper-scissors tournament is encoded as an array of games - that is, each element can be considered its own tournament.

    [
      [
        [ ["Armando", "P"], ["Dave", "S"] ],      
        [ ["Richard", "R"], ["Michael", "S"] ]
      ],
      [
        [ ["Allen", "S"], ["Omer", "P"] ],
        [ ["David E.", "R"], ["Richard X.", "P"] ]
      ]
    ]

Under this scenario, Dave would beat Armando (S>P) and Richard would beat Michael (R>S), so Dave and Richard would play (Richard wins since R>S); similarly, Allen would beat Omer, David E. would beat Richard X., and Allen and Richard X. would play (Allen wins since S>P); and finally Richard would beat Allen since R>P. That is, pairwise play continues until there is only a single winner.

Write a method `RockPaperScissors.tournament_winner' that takes a tournament encoded as an array and returns the winner (for the above example, it should return ['Richard', 'R']). You can assume that the array is well formed (that is, there are 2^n players, and each one participates in exactly one match per round).

HINT: Formulate the problem as a recursive one whose base case you solved in part 1.