From: Ruby Quiz <james@...>
Date: 2007-03-02T22:34:38+09:00
Subject: [QUIZ] GOPS (#116)

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by Christoffer Lerno

GOPS, the Game of Pure Strategy (a.k.a Goofspiel), is a very simple cardgame.

In GOPS, one suit is singled out as "competition suit" and each of the remaining
suits becomes the hand for a player (with one suit discarded if there are only
two players). The competition suit is shuffled and placed face down.

Game starts by turning up the top card in the competition stack. The players
then make a hidden bid on the card, using one of their own cards. Once all
players have made a bid, the cards are revealed and the player with the highest
card collects the competition card. In case of a tie, the competition card is
discarded.

The game then proceeds in the same manner until the competition stack is empty.

The winner is the player with the highest number of points calculated from the
competition cards won, where Ace is the lowest--worth 1 point--and King is the
highest--worth 13 points.

The task for this quiz is to write a bot to play 2-player GOPS against other
bots.

A bot needs to be able to read gameplay on STDIN and write its moves to STDOUT
using the following protocol:

	1. The engine sends the first competition card as the string "Competition
	   card: CARD", where CARD is the value of the card, from 1 (Ace) to 13
	   (King).
	   
	   Example: The server would write "Competition card: 12" if the competition
	   card for this round was Queen of the competition suit.
	
	2. The engine then expects a response within 30 seconds. The response should
	   be the value of the card you wish to play as a string.  You may only play
	   each card in your suit once, of course.
	
	   Example: The bot could print the line "10" to STDOUT (and flush output)
	   to bid with a ten.
	
	3. The engine will respond by sending the card the opponent just played as
	   the string "Opponent's bid:  CARD" where CARD is the value of the bid
	   (1-13).
	
	   Example, the engine would print "Opponent's bid:  3" if the opponent bid
	   a 3 in the last round.  This tells you that your 10 beat the opponent's
	   3 and you won the Queen.
	
	4. Return to 1 with the next card in the competition stack, until all 13
	   cards have been played.

Here is a very simple random bot implementing the protocol:

	(1..13).sort_by { rand }.each do |card|
	  $stdin.gets # competition card--ignored
	  $stdout.puts card
	  $stdout.flush
	  $stdin.gets # opponent's play--ignored
	end

A GOPS engine and some trivial bots are available for you to use in testing your
strategies:

	http://rubyquiz.com/gops.zip