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 Who will win? (Posted on 2005-01-10)
There are 2n cards labeled 1, 2, ..., 2n respectively, and the cards are distributed randomly between two players so that each has n cards. Each player takes turns to place one card, and you win if you put down a card so that the current sum of all the played cards is divisible by 2n+1.

For example, if n=10, and the previously placed cards are 5, 8, 9, 19, then if player A now places 1, he wins since 5+8+9+19+1 = 42 is divisible by 2*10+1=21.

Assuming both players want to win, what strategy should one adopt in order to win? Following the strategy, is there a consistent winner of this game?

 See The Solution Submitted by Bon Rating: 2.0000 (1 votes)

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 re(4): Solution | Comment 6 of 9 |
(In reply to re(3): Solution by Charlie)

There is no need to follow the decision tree to the end of the game.  A local decision suffices:  simply make a move that does not result in an immediate win for Player 1.

 Posted by David Shin on 2005-01-10 19:40:00

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