Beggar-My-Neighbour

From Wikipedia, the free encyclopedia

Beggar-My-Neighbour, also known as Beat Jack Out of Doors, Beat Your Neighbour Out of Doors, Strip Jack Naked and Draw the Well Dry, is a simple card game somewhat similar in nature to War, and has spawned a more complicated variant, Egyptian Ratscrew. It was likely invented in Britain and has been known there since at least the 1860s. It appears in Charles Dickens's 1861 novel Great Expectations, as the only card game Pip, the book's protagonist, as a child seems to know how to play.

A standard 52-card deck is divided equally between two players, and the two stacks of cards are placed on the table with the backs upwards. The first player lays down his top card face up, and the opponent plays his top card on it, and this goes on alternately as long as no ace or face card (king, queen, or jack) appears.

If either player turns up such a card, his opponent has to pay a penalty: four cards for an ace, three for a king, two for a queen, or one for a jack. When he has done so, the player of the penalty card takes all the cards in the pile and places them under his pack and the game continues as normal. However, if the second player turns up another ace or face card in the course of paying to the original penalty card, his payment ceases and the first player must pay to this new card. This changing of penalization can continue indefinitely. When one player can find nothing and loses the hand, his opponent acquires all of the cards in the pile.

Unsolved problems in mathematics: Is there a non-terminating game of Beggar-My-Neighbour?

When a single player has all of the cards in the deck in his stack, he has won.

A longstanding question in combinatorial game theory asks whether there is a game of Beggar-My-Neighbour which goes on forever. This can happen only if the game is eventually periodic—that is, if it eventually reaches some state it has been in before. Some smaller decks of cards have infinite games, while others do not. John Conway once listed this among his anti-Hilbert problems, open questions whose pursuit should emphatically not drive the future of mathematical research.