Nim

Nim is a strategy game between two players.

  1. Start by placing counters (coins or toothpicks or something) into 3 piles.
  2. Player #1 picks a pile, then removes one or more counters from that pile. (It's okay to take the whole pile.)
  3. Player #2 picks a pile, then removes one or more counters from that pile.
  4. Player #1 plays again. (It's okay to choose a different pile this time.)
  5. Whichever player is forced to take the last counter is the LOSER.

Write a program that allows two human players to play Nim against each other. The program should detect when the last counter has been taken and declare a winner.

At first, don't worry about detecting cheating. That is one of the bonus options.

If you do any of the bonus, please add a comment at the top explaining which bonus options you did and how many points you expect.

Sample Output

Here is an example game, with starting piles of 3, 4, and 5 counters.

Player 1, enter your name: Alice
Player 2, enter your name: Bob

A: 3	B: 4	C: 5

Alice, choose a pile: A
How many to remove from pile A: 2

A: 1	B: 4	C: 5

Bob, choose a pile: C
How many to remove from pile C: 3

A: 1	B: 4	C: 2

Alice, choose a pile: B
How many to remove from pile B: 1

A: 1	B: 3	C: 2

Bob, choose a pile: B
How many to remove from pile B: 1

A: 1	B: 2	C: 2

Alice, choose a pile: A
How many to remove from pile A: 1

A: 0	B: 2	C: 2

Bob, choose a pile: B
How many to remove from pile B: 1

A: 0	B: 1	C: 2

Alice, choose a pile: C
How many to remove from pile C: 2

A: 0	B: 1	C: 0

Bob, choose a pile: B
How many to remove from pile B: 1

A: 0	B: 0	C: 0

Alice, there are no counters left, so you WIN!

Bonus #1 - Cheat Protection

For +30 bonus points, prevent the users from doing anything bad:

...a game already in progress.

A: 0	B: 1	C: 0

Bob, choose a pile: A

Nice try, Bob. That pile is empty. Choose again: B
How many to remove from pile B: 0

You must choose at least 1. How many? 1

A: 0	B: 0	C: 0

And what about this?

A: 1	B: 4	C: 5

Bob, choose a pile: C
How many to remove from pile C: 8

Pile C doesn't have that many. Try again: 3

A: 1	B: 4	C: 2

And don't forget this:

A: 1	B: 4	C: 5

Bob, choose a pile: C
How many to remove from pile C: -2

You must choose at least 1. How many? 3

A: 1	B: 4	C: 2

Bonus #2 - Dignity

For +10 bonus points, make your program detect when there is only one counter left and declare the winner one turn earlier.

...a game already in progress.

A: 0	B: 2	C: 2

Bob, choose a pile: B
How many to remove from pile B: 1

A: 0	B: 1	C: 2

Alice, choose a pile: C
How many to remove from pile C: 2

A: 0	B: 1	C: 0

Bob, you must take the last remaining counter, so
you lose. Alice wins!

Bonus #3 - Fancy Display (Rows)

For +15 bonus points, visually display the counters in rows instead of just showing a number. You must use loops for this.

A: ***
B: ****
C: *****

Alice, choose a pile: A
How many to remove from pile A: 2

A: *
B: ****
C: *****

Bob, choose a pile: C
How many to remove from pile C: 3

A: *
B: ****
C: **

Bonus #4 - Fancy Display (Columns)

For +25 bonus points, visually display the counters in columns. You must use a loop for this.

This is quite difficult.

        *
      * *
    * * *
    * * *
    * * *
    A B C

Alice, choose a pile: A
How many to remove from pile A: 2

        *
      * *
      * *
      * *
    * * *
    A B C

Bob, choose a pile: C
How many to remove from pile C: 3
 
      * 
      * 
      * *
    * * *
    A B C

Bonus #5 - Computer Opponent

For +50 bonus points, allow one human player to play against a computer opponent. The computer must attempt to win and not break any rules.

It is possible to make a computer player that ALWAYS wins if it goes first. The Wikipedia article for Nim explains the theory.

However, your program does not need to use a winning strategy to earn bonus points: it merely must make only legal moves.

©2013–2015 Graham Mitchell

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