Intermediate Exercism • go

Camicia

Challenge Overview

Simulate the card game and determine whether the match ends or enters an infinite loop.

Introduction

One rainy afternoon, you sit at the kitchen table playing cards with your grandmother. The game is her take on Camicia.

At first it feels like just another friendly match: cards slapped down, laughter across the table, the occasional victorious grin from Nonna. But as the game stretches on, something strange happens. The same cards keep cycling back. You play card after card, yet the end never seems to come.

You start to wonder. Will this game ever finish? Or could we keep playing forever?

Later, driven by curiosity, you search online and to your surprise you discover that what happened wasn’t just bad luck. You and your grandmother may have stumbled upon one of the longest possible sequences! Suddenly, you’re hooked. What began as a casual game has turned into a quest: how long can such a game really last? Can you find a sequence even longer than the one you played at the kitchen table? Perhaps even long enough to set a new world record?

And so, armed with nothing but a deck of cards and some algorithmic ingenuity, you decide to investigate…

Instructions

In this exercise, you will simulate a game very similar to the classic card game Camicia. Your program will receive the initial configuration of two players’ decks and must simulate the game until it ends (or detect that it will never end).

Rules

The deck is split between two players. The player’s cards are read from left to right, where the leftmost card is the top of the deck.
A round consists of both players playing at least one card.
Players take turns placing the top card of their deck onto a central pile.
If the card is a number card (2-10), play simply passes to the other player.
If the card is a payment card, a penalty must be paid:
- J → opponent must pay 1 card
- Q → opponent must pay 2 cards
- K → opponent must pay 3 cards
- A → opponent must pay 4 cards
If the player paying a penalty reveals another payment card, that player stops paying the penalty. The other player must then pay a penalty based on the new payment card.
If the penalty is fully paid without interruption, the player who placed the last payment card collects the central pile and places it at the bottom of their deck. That player then starts the next round.
If a player runs out of cards and is unable to play a card (either while paying a penalty or when it is their turn), the other player collects the central pile.
The moment when a player collects cards from the central pile is called a trick.
If a player has all the cards in their possession after a trick, the game ends.
The game enters a loop as soon as the decks are identical to what they were earlier during the game, not counting number cards!

Examples

A small example of a match that ends.

Round	Player A	Player B	Pile	Penalty Due
1	2 A 7 8 Q 10	3 4 5 6 K 9 J		-
1	A 7 8 Q 10	3 4 5 6 K 9 J	2	-
1	A 7 8 Q 10	4 5 6 K 9 J	2 3	-
1	7 8 Q 10	4 5 6 K 9 J	2 3 A	Player B: 4
1	7 8 Q 10	5 6 K 9 J	2 3 A 4	Player B: 3
1	7 8 Q 10	6 K 9 J	2 3 A 4 5	Player B: 2
1	7 8 Q 10	K 9 J	2 3 A 4 5 6	Player B: 1
1	7 8 Q 10	9 J	2 3 A 4 5 6 K	Player A: 3
1	8 Q 10	9 J	2 3 A 4 5 6 K 7	Player A: 2
1	Q 10	9 J	2 3 A 4 5 6 K 7 8	Player A: 1
1	10	9 J	2 3 A 4 5 6 K 7 8 Q	Player B: 2
1	10	J	2 3 A 4 5 6 K 7 8 Q 9	Player B: 1
1	10	-	2 3 A 4 5 6 K 7 8 Q 9 J	Player A: 1
1	-	-	2 3 A 4 5 6 K 7 8 Q 9 J 10	-
2	-	2 3 A 4 5 6 K 7 8 Q 9 J 10	-	-

status: "finished", cards: 13, tricks: 1

This is a small example of a match that loops.

Round	Player A	Player B	Pile	Penalty Due
1	J 2 3	4 J 5	-	-
1	2 3	4 J 5	J	Player B: 1
1	2 3	J 5	J 4	-
2	2 3 J 4	J 5	-	-
2	3 J 4	J 5	2	-
2	3 J 4	5	2 J	Player A: 1
2	J 4	5	2 J 3	-
3	J 4	5 2 J 3	-	-
3	J 4	2 J 3	5	-
3	4	2 J 3	5 J	Player B: 1
3	4	J 3	5 J 2	-
4	4 5 J 2	J 3	-	-

The start of round 4 matches the start of round 2. Recall, the value of the number cards does not matter.

status: "loop", cards: 8, tricks: 3

Your Task

Using the input, simulate the game following the rules above.
Determine the following information regarding the game:
- Status: "finished" or "loop"
- Cards: total number of cards played throughout the game
- Tricks: number of times the central pile was collected

For those who want to take on a more exciting challenge, the hunt for other records for the longest game with an end is still open.
There are 653,534,134,886,878,245,000 (approximately 654 quintillion) possibilities, and we haven't calculated them all yet!

Source: Exercism go/camicia