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06-27-24 04:15 PM
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Acmlm's Board - I3 Archive - Brain Teasers - ||bass' Impossible Yet Possible Quiz - Question 2 (Coin Game)
  
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||bass
Posts: 12/594
Ok. That was better then last time.

drizzt do'urden's answer is WRONG for making assumptions about things I didn't mention in the question.

Cellar Dweller's answer is CORRECT. The proper strategy is to, on your turn, always return the coin count to a multiple of 3 by drawing however many coins are required to do so.
Cellar Dweller +
Posts: 13/138
For each turn, draw however many coins is needed to force the number of coins in the pile to a multiple of three (zero inclusive, of course).

I solved this by making a list of numbers and assigning an advantage to a player. 1, 2, and 4, were assigned to the current player, and 3 was assigned to the next player. By manualy going through the possible moves, I assigned advantages up to about 6, when I saw that the advantage would always go the next player if there was a multiple of 3 coins in the pile. Shortly after that, I realized that the choices of numbers of coins to remove made it possible for a player to force the number of coins on the pile to a multiple of 3 as long as there is not a multiple of 3 coins in the pile.
drizzt do'urden
Posts: 10/57
P1: 2 coins
P2: 4 coins
P1: 2 coins
P2: 4 coins
P1: 2 coins
P2: 4 coins
P1: 2 coins
P2: 4 coins
P1: 2 coins
P2: 4 coins
P1: 2 coins
P2: 4 coins
P1: 2 coins
P2: 1 coin
P1: 1 coin

Player 1 takes out 2 coins every turn while player 2 takes out 4 coins until there is 2 coins left in which they will both take just 1 coin out each. Player 1 will take the final coin.
||bass
Posts: 11/594
Ok. Since you all did so poorly on the last question. I've decided to have a much easier question this time.

The Coin Game:
The rules are as follows
The game has 2 players, alternating turns.
You begin with a pile of 40 coins.
On each turn, a player may remove 1,2 or 4 coins.
The player to remove the LAST coin wins.

Find a strategy that is guarinteed to win for the FIRST player.
Acmlm's Board - I3 Archive - Brain Teasers - ||bass' Impossible Yet Possible Quiz - Question 2 (Coin Game)


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