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Alice and Bob play the following coins-on-a-stack game. 20
coins are stacked one above the other. One of them is a
special (gold) coin and the rest are ordinary coins. The
goal is to bring the gold coin to the top by repeatedly
moving the topmost coin to another position in the stack.
Alice starts and the players take turns. A turn consists of
moving the coin on the top to a position i below the top
coin (0 = i = 20). We will call this an i-move (thus a 0-
move implies doing nothing). The proviso is that an i-move
cannot be repeated; for example once a player makes a 2-
move, on subsequent turns neither player can make a 2-move.
If the gold coin happens to be on top when it's a player's
turn then the player wins the game. Initially, the gold
coinis the third coin from the top
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Answer / abhishek
if Alice takes 0: then 2 coins left over gold, now B takes
>=2 then 1 coin left above gold..Alice cannot take 0..any
other will make the gold at top. so not 0
If alice takes 1 at first then 2 coins left. . now B can
take 0 or anything >=2.
If B takes 0,then no change..now A takes 2 leaving 1 coin
above gold..what ever b takes A wins.
If B takes 2 then one coin left above gold then A takes
zero.. now what ever B takes A wins
So 1 first
| Is This Answer Correct ? | 20 Yes | 0 No |
Answer / teena
alice can take either a 0move or a 1 move.
initially if alice take 0 then bob take 1.. which means there are still 2 coins above the gold coin... the same is true when alice takes 1 and bob take zero...
after this alice choise must be 2.. so there is one coin above the gold coin... so then watever choice bob makes brings the coin to position 1...
ao alice is the winner
| Is This Answer Correct ? | 29 Yes | 13 No |
Answer / sarath chandra
Case 1:suppose Alice starts with a 0 move.Now bob cleverly
goes for a 2 move so that there is only one coin above the
gold coin.Now irrespective of alice's move Bob wins.
Case 2:suppose alice stats with a 1 move it barely makes any
difference.Again Bob goes for a 2 move and he wins.
So alice has no winning strategy at all.Hence
pavan got it right
| Is This Answer Correct ? | 15 Yes | 10 No |
Answer / adarsh j
Answer is if alice start with 1 then it is correct bcoz
if alice starts wid 1 thn bob choses 2
then he wid 3 bob choses 4
aslike.
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atlast alice gets the gold coin
| Is This Answer Correct ? | 13 Yes | 20 No |
Answer / pavankumar srikanta
there is no winning strategy for Alice.
| Is This Answer Correct ? | 24 Yes | 34 No |
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