Nim game
Nim is a simple game where the second player - if they know the trick - will always win. The game has only 3 rules.
- start with 12 tokens
- each player takes 1, 2, or 3 tokens in turn
- the player who takes the last token wins.
To win every time, the second player simply takes 4 minus the number the first player took. So if the first player takes 1, the second takes 3 - if the first player takes 2, the second should take 2 - and if the first player takes 3, the second player will take 1.
- Task
Design a simple Nim game where the player goes first, and the computer always wins. The game should enforce the rules.
AsciiDots
<lang AsciiDots> %$MXTRL .-$"Nim Dots"-$""-
/$_"Number must be "\
T /----~------\ |
*M /---+-*-[o] | |
R [-]\ .>#3-+[>][<]-1#<.| |
.-#12>--^ \"stod "$-#_$-" ekat uoY"_$---/ \--*----*-/ |
.>$_"How many dots would you like to take"---#?---/ |
\X X---------<".3 dna 1 neewteb"$/
/-----*L |
[-]--\ R |
| *-$_"Computer takes "-$_#-$" dots"/
M-*#4[%]
\---/
/----------------$"computer wins!"-&
/---~--
*#0[=]
L-------------*---*>$_#-$" dots remaining."-$""
T
</lang>
- Output:
Nim Dots v0.5 by Prof_Apex How many dots would you like to take?: 3 You take 3 dots 9 dots remaining. Computer takes 1 dots 8 dots remaining. How many dots would you like to take?: 1 You take 1 dots 7 dots remaining. Computer takes 3 dots 4 dots remaining. How many dots would you like to take?: 2 You take 2 dots 2 dots remaining. Computer takes 2 dots 0 dots remaining. computer wins!
C++
<lang cpp>#include <iostream>
- include <limits>
using namespace std;
void showTokens(int tokens) {
cout << "Tokens remaining " << tokens << endl << endl;
}
int main() {
int tokens = 12;
while (true) {
showTokens(tokens);
cout << " How many tokens 1, 2 or 3? ";
int t;
cin >> t;
if (cin.fail()) {
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
cout << endl << "Invalid input, try again." << endl << endl;
} else if (t < 1 || t > 3) {
cout << endl << "Must be a number between 1 and 3, try again." << endl << endl;
} else {
int ct = 4 - t;
string s = (ct > 1) ? "s" : "";
cout << " Computer takes " << ct << " token" << s << endl << endl;
tokens -= 4;
}
if (tokens == 0) {
showTokens(0);
cout << " Computer wins!" << endl;
return 0;
}
}
}</lang>
- Output:
Sample game:
Tokens remaining 12 How many tokens 1, 2 or 3? nim Invalid input, try again. Tokens remaining 12 How many tokens 1, 2 or 3? 1 Computer takes 3 tokens Tokens remaining 8 How many tokens 1, 2 or 3? 0 Must be a number between 1 and 3, try again. Tokens remaining 8 How many tokens 1, 2 or 3? 2 Computer takes 2 tokens Tokens remaining 4 How many tokens 1, 2 or 3? 3 Computer takes 1 token Tokens remaining 0 Computer wins!
Common Lisp
<lang lisp> (defun pturn (curTokens) (write-string "How many tokens would you like to take?: ") (setq ans (read)) (setq tokensRemaining (- curTokens ans)) (format t "You take ~D tokens~%" ans) (printRemaining tokensRemaining) tokensRemaining)
(defun cturn (curTokens) (setq take (mod curTokens 4)) (setq tokensRemaining (- curTokens take)) (format t "Computer takes ~D tokens~%" take) (printRemaining tokensRemaining) tokensRemaining)
(defun printRemaining (remaining) (format t "~D tokens remaining~%~%" remaining))
(format t "LISP Nim~%~%")
(setq tok 12)
(loop
(setq tok (pturn tok))
(setq tok (cturn tok))
(if (<= tok 0)
(return)))
(write-string "Computer wins!")
</lang>
- Output:
LISP Nim How many tokens would you like to take?: 2 You take 2 tokens 10 tokens remaining Computer takes 2 tokens 8 tokens remaining How many tokens would you like to take?: 1 You take 1 tokens 7 tokens remaining Computer takes 3 tokens 4 tokens remaining How many tokens would you like to take?: 3 You take 3 tokens 1 tokens remaining Computer takes 1 tokens 0 tokens remaining Computer wins!
Go
<lang go>package main
import (
"bufio" "fmt" "os" "strconv"
)
func showTokens(tokens int) {
fmt.Println("Tokens remaining", tokens, "\n")
}
func main() {
tokens := 12
scanner := bufio.NewScanner(os.Stdin)
for {
showTokens(tokens)
fmt.Print(" How many tokens 1, 2 or 3? ")
scanner.Scan()
if scerr := scanner.Err(); scerr != nil {
fmt.Println("Error reading standard input:", scerr)
return
}
t, err := strconv.Atoi(scanner.Text())
if err != nil || t < 1 || t > 3 {
fmt.Println("\nMust be a number between 1 and 3, try again.\n")
} else {
ct := 4 - t
s := "s"
if ct == 1 {
s = ""
}
fmt.Print(" Computer takes ", ct, " token", s, "\n\n")
tokens -= 4
}
if tokens == 0 {
showTokens(0)
fmt.Println(" Computer wins!")
return
}
}
}</lang>
- Output:
Sample game:
Tokens remaining 12 How many tokens 1, 2 or 3? 2 Computer takes 2 tokens Tokens remaining 8 How many tokens 1, 2 or 3? 4 Must be a number between 1 and 3, try again. Tokens remaining 8 How many tokens 1, 2 or 3? 1 Computer takes 3 tokens Tokens remaining 4 How many tokens 1, 2 or 3? 3 Computer takes 1 token Tokens remaining 0 Computer wins!
Kotlin
<lang scala>// Version 1.3.21
fun showTokens(tokens: Int) {
println("Tokens remaining $tokens\n")
}
fun main() {
var tokens = 12
while (true) {
showTokens(tokens)
print(" How many tokens 1, 2 or 3? ")
var t = readLine()!!.toIntOrNull()
if (t == null || t < 1 || t > 3) {
println("\nMust be a number between 1 and 3, try again.\n")
} else {
var ct = 4 - t
var s = if (ct > 1) "s" else ""
println(" Computer takes $ct token$s\n")
tokens -= 4
}
if (tokens == 0) {
showTokens(0)
println(" Computer wins!")
return
}
}
}</lang>
- Output:
Sample game:
Tokens remaining 12 How many tokens 1, 2 or 3? 3 Computer takes 1 token Tokens remaining 8 How many tokens 1, 2 or 3? nim Must be a number between 1 and 3, try again. Tokens remaining 8 How many tokens 1, 2 or 3? 2 Computer takes 2 tokens Tokens remaining 4 How many tokens 1, 2 or 3? 1 Computer takes 3 tokens Tokens remaining 0 Computer wins!
Python
<lang Python> print("Py Nim\n")
def getTokens(curTokens): global tokens
print("How many tokens would you like to take? ", end=) take = int(input())
if (take < 1 or take > 3): print("Number must be between 1 and 3.\n") getTokens(curTokens) return
tokens = curTokens - take print(f'You take {take} tokens.') print(f'{tokens} tokens remaining.\n')
def compTurn(curTokens): global tokens
take = curTokens % 4 tokens = curTokens - take print (f'Computer takes {take} tokens.') print (f'{tokens} tokens remaining.\n')
tokens = 12
while (tokens > 0):
getTokens(tokens)
compTurn(tokens)
print("Computer wins!") </lang>
- Output:
Py Nim 0.5 by Prof_Apex How many tokens would you like to take? 2 You take 2 tokens. 10 tokens remaining. Computer takes 2 tokens. 8 tokens remaining. How many tokens would you like to take? 1 You take 1 tokens. 7 tokens remaining. Computer takes 3 tokens. 4 tokens remaining. How many tokens would you like to take? 3 You take 3 tokens. 1 tokens remaining. Computer takes 1 tokens. 0 tokens remaining. Computer wins!