Computer Science Canada

The game of Nim starts with a random number of stones between 15 and 30. Two players alternates turns and on each turn may take either 1, 2 or 3 stones from the pile. The player forced to take the last stone loses. Create a Nim application that allows the user to play against the computer. In this version of the game, the application generates the number of stones to begin with, the number of stones the computer takes and the user goes first.

Include code that prevents the user and computer from taking an illegal num ber of stones. For example, neither should be allowed to take three stones when there are only 1 or 2 left. Your program should use:

Â· A valid entry function to check the number entered by the user.

Â· The randint function to generate a random number between 1 and 3 for the computer's turn

Â· Separate procedures for the user's turn and the computer's turn.

var TotGen, Turn, PInput, CompTake : int := 0
var Flag := false

TotGen := Rand.Int (15, 30)

proc CheckWin
if TotGen = 1 then
put "You Lose! " ..
if Turn mod 2 = 0 then
put "Computer"
else
put "Player"
end if
Flag := true
end if
end CheckWin

fcn AIGetTempTotal : int
for rep : 0 .. 7
if TotGen - ((4 * rep) + 1) < 4 then
result (4 * rep) + 1
end if
end for
end AIGetTempTotal

loop
CheckWin
exit when Flag = true

put "We now have ", TotGen, " stones left"
put "It's now the computer's turn"

if TotGen - AIGetTempTotal not= 0 then
CompTake := TotGen - AIGetTempTotal
TotGen -= CompTake
else
CompTake := Rand.Int (1, 3)
TotGen -= CompTake
end if
put "Computer takes ", CompTake, " stones.\n"
Turn += 1

CheckWin
exit when Flag = true

put "it's now the player's turn"
put "We now have ", TotGen, " stones left"
loop
put "Player, please take 1, 2, or 3 stones from the pile: " ..
get PInput
if PInput > 3 or PInput < 1 then
put "Invalid move, try again!"
else
exit
end if
end loop
put skip
TotGen -= PInput
Turn += 1
end loop

Author:	AsianSensation [ Sat Nov 15, 2003 1:43 pm ]
Post subject:
cool, this is like an old Euclid question or something like that. anyways, suppose there are 5 stones, and computer goes first, then obviously the human player wins. now if we have 4k + 1 stones, where k is an integer, such as 17 stones, and computer go first, then the human player will always win also. Because whatever the computer takes, the player may take 4 minus that number, to bring the total down to another multiple of 4 plus 1. So therefore, it's possible to see that whenever it's a person's move, and they have a multiple of 4 plus 1 stones left to take from, then they will lose. So all you have to do for your AI is to make sure he takes enough stones such that 4k + 1 stones will be left after the AI finishes it's move. Needless to say, that if you generate a multiple of 4 plus 1 to begin with, then your AI will always lose, assuming perfect game played by the player

Author:	RETARD32 [ Sat Nov 15, 2003 1:51 pm ]
Post subject:
Here's my stab at it, the a.i. , I think could be improved a bit var stones, p1, p2, lose : int randint (stones, 15, 30) fcn checkit (p1, stones : int) : int if p1 > 3 or p1 > stones then put "Invalid Input" result stones - 0 else result stones - p1 end if end checkit proc human put "How many stones? (max 3)" loop get p1 stones := checkit (p1, stones) exit when p1=1 exit when p1=2 exit when p1=3 end loop end human proc cpu if stones = 2 then p1 := 1 elsif stones = 1 then p1 := 1 elsif stones / 2 = stones div 2 then p1 := 1 elsif stones = 4 then p1 := 3 elsif stones = 3 then p1 := 2 else randint (p1, 1, 3) end if stones := checkit (p1, stones) put "CPU takes:", p1 put " " delay (1000) end cpu proc showstone locate (1, 35) put "Total stones : ", stones end showstone loop showstone human if stones = 0 then lose := 1 end if exit when stones = 0 showstone cpu if stones = 0 then lose := 2 end if exit when stones = 0 cls end loop if lose = 1 then cls put "YOU LOSE!" elsif lose = 2 then cls put "YOU WIN!" end if