Trick-Taking Game

Card Game Cheating by Caravaggio

This is a simple card game in form of interactive problems - hopefully you already solved some of them.

As the problem is based upon a game with some randomness and "imperfect information", you may need to retry a few times even with "potentially winning" strategy. Many thanks to Clive Fraser for help in improving these aspects.

Game Setup and Rules

Two players use a deck of 36 cards, arranged in 4 suits (WXYZ) and 9 ranks (012345678). Both sets of symbols are slightly uncommon, but "consecutive" in the sense of ASCII, which may simplify coding.

To start, each player gets a "hand" of 9 random cards, remaining 18 are left in a single pack on a table, their backs up. One of the suits is chosen trump, except the case when no-trump game is played.

Game is played in rounds, in which one player chooses a card to attack and the other chooses a card to defend (both from their respecitve "hand"). If the defender's card is of same suit, but higher rank - or defender's card is of a trump suit while attacker's is not - in both such cases defender scores this "trick". Otherwise it is scored to attacker.

Additional rule is that defender should "follow suit" of attacker - i.e. respond with the same-suit card if possible. However in the absense of the suitable suit playing with trump is not obligatory.

After each round two cards are dealt from the pack on the table, if it is not exhausted yet. So players keep the hand of 9 cards during first 10 rounds, while remaining 8 rounds are played with steadily decreasing hand.

First to attack is chosen randomly, but after that the attacker is always those who have won the previous trick.

The game is won by whoever scores more tricks.

Technical Details

GAME-NAME is tricks - use it in the server url given in the instruction above.

Input data gives you a token to play and answer should contain victory token returned to you by server (while the game is in test mode you'll never get it).

You are playing several simultaneous games however. They use separate decks, so they are completely independent.

Every turn server will respond you with states variable, which contains space-separated chunks of symbols describing latest changes in every on N simultaneously played games.

Immediately after start there'll be also sequence of card's in your hands and trump suit separated by colon, e.g.

Z1X1Y1Z2Z0Y5W3:X - you get cards Z1,X1,Y1,Z2,Z0,Y5,W3 and X suit is trump

No-trump game is denoted by letter N.

The game actions are denoted by the following fragments:

• symbol > followed by card - means this card is played by your opponent
• symbols + or - mean the outcome of defend - either you have won the trick or not
• these symbols are followed by the card denoting what you get from the pack to replenish your hand

These fragments are chained in the natural order of actions in the game. Let's look at few examples:

• >X6-W3>Y4 - your opponent played X6 and it was defence, since next is - meaning you lost the trick; you got W3 from the pack and your opponent attacks with Y4; it's your turn to defend now
• >X1+Z0 - your opponent played X1 and it was defence, since next is + meaning you won the trick; you got Z0 from the pack and it is your turn to attack now
• + - your last played card was defence and it was successful, you won the trick and you got nothing from the pack (because it is exhausted); it is your turn to attack

Initial state with description of your hand is immediately followed by > and some card if your opponent is the first to attack. Otherwise it is you to attack first.

Your moves are specified by move variable in the request, containing N cards separated by space - whatever cards you choose to play in each of N simultaneous games. Be careful - failure to follow suit, or naming the card which you don't have in hand at all - both are considered grave mistakes and corresponding game is ended immediately with all remaining tricks awarded to your opponent.

Besides token you can specify _games variable, integer, which defines how many simultaneous games to play, default is 3 but you can reduce it to 1 to facilitate manual play for example.

Winning Condition

After all games have ended, your overall score is calculated as +1 for every game won and -1 for every game lost (0 for draws). To win you need the overall score of 35 or higher. This means you'll need to set _games parameter to 35 at least (maximum is 200 games).

Example

Suppose you test the game manually using curl command line tool:

Request (with "form-data" format):

curl <server>/tricks.php -d 'token=...&_games=2'

Response:

states: Z2X0Z7W6Z1Z3W3X2W8:N Z5Y0Y5W4Z4X7Y2Y3Y7:X>Z0
scores: 0:0 0:0

Here the first of two games is no-trump, the second has X as trumps. Also in the first you are to attack while in the second your opponent attacks with Z0.

Request, sending cards to play on both tables:

curl <server>/tricks.php -d 'token=...&move=W6 Z5'

Response:

states: >W4+Y1 +X6
scores: 0:1 0:1

Thus on the first table your opponent passed with W4, you won the trick, got Y1 from pack and is expected to attack on the next move. On the second table you won the trick (you were defending) and got X6 and also is expected to attack.