Bulls and cows
This is an old game played with pencil and paper that was later implemented on computer.
You are encouraged to solve this task according to the task description, using any language you may know.
The task is for the program to create a four digit random number from the digits 1 to 9, without duplication. The program should ask for guesses to this number, reject guesses that are malformed, then print the score for the guess.
The score is computed as:
- The player wins if the guess is the same as the randomly chosen number, and the program ends.
- A score of one bull is accumulated for each digit in the guess that equals the corresponding digit in the randomly chosen initial number.
- A score of one cow is accumulated for each digit in the guess that also appears in the randomly chosen number, but in the wrong position.
C
<lang c>#include <stdio.h>
- include <stdarg.h>
- include <stdlib.h>
- include <stdbool.h>
- include <curses.h>
- include <string.h>
- define MAX_NUM_TRIES 72
- define LINE_BEGIN 7
- define LAST_LINE 18
int yp=LINE_BEGIN, xp=0;
char number[5]; char guess[5];
- define MAX_STR 256
void mvaddstrf(int y, int x, char *fmt, ...) {
va_list args; char buf[MAX_STR]; va_start(args, fmt); vsprintf(buf, fmt, args); move(y, x); clrtoeol(); addstr(buf); va_end(args);
}
void ask_for_a_number() {
int i=0; char symbols[] = "123456789";
move(5,0); clrtoeol();
addstr("Enter four digits: ");
while(i<4) {
int c = getch();
if ( (c >= '1') && (c <= '9') && (symbols[c-'1']!=0) ) {
addch(c);
symbols[c-'1'] = 0;
guess[i++] = c;
}
}
}
void choose_the_number() {
int i=0, j; char symbols[] = "123456789";
while(i<4) {
j = rand() % 9;
if ( symbols[j] != 0 ) {
number[i++] = symbols[j];
symbols[j] = 0;
}
}
}</lang>
The following function contains the code to check how many bulls and cows there are.
<lang c>bool take_it_or_not() {
int i; int cows=0, bulls=0;
for(i=0; i < 4; i++) {
if ( number[i] == guess[i] ) {
bulls++;
} else if ( strchr(number, guess[i]) != NULL ) {
cows++;
}
}
move(yp, xp);
addstr(guess); addch(' ');
if ( bulls == 4 ) { yp++; return true; }
if ( (cows==0) && (bulls==0) ) addch('-');
while( cows-- > 0 ) addstr("O");
while( bulls-- > 0 ) addstr("X");
yp++;
if ( yp > LAST_LINE ) {
yp = LINE_BEGIN;
xp += 10;
}
return false;
}
bool ask_play_again() {
int i;
while(yp-- >= LINE_BEGIN) {
move(yp, 0); clrtoeol();
}
yp = LINE_BEGIN; xp = 0;
move(21,0); clrtoeol();
addstr("Do you want to play again? [y/n]");
while(true) {
int a = getch();
switch(a) {
case 'y':
case 'Y':
return true;
case 'n':
case 'N':
return false;
}
}
}
int main()
{
bool bingo, again; int tries = 0;
initscr(); cbreak(); noecho(); clear();
number[4] = guess[4] = 0;
mvaddstr(0,0, "I choose a number made of 4 digits (from 1 to 9) without repetitions\n"
"You enter a number of 4 digits, and I say you how many of them are\n"
"in my secret number but in wrong position (cows or O), and how many\n"
"are in the right position (bulls or X)");
do {
move(20,0); clrtoeol(); move(21, 0); clrtoeol();
srand(time(NULL));
choose_the_number();
do {
ask_for_a_number();
bingo = take_it_or_not();
tries++;
} while(!bingo && (tries < MAX_NUM_TRIES));
if ( bingo )
mvaddstrf(20, 0, "You guessed %s correctly in %d attempts!", number, tries);
else
mvaddstrf(20,0, "Sorry, you had only %d tries...; the number was %s",
MAX_NUM_TRIES, number);
again = ask_play_again(); tries = 0; } while(again); nocbreak(); echo(); endwin(); return EXIT_SUCCESS;
}</lang>
Java
<lang java5>import java.util.InputMismatchException; import java.util.Random; import java.util.Scanner;
public class BullsAndCows{ public static void main(String[] args){ Random gen= new Random(); int target= 0; while(hasDupes(target= (gen.nextInt(9000) + 1000))); String targetStr = target +""; boolean guessed = false; Scanner input = new Scanner(System.in); int guesses = 0; do{ int bulls = 0; int cows = 0; System.out.print( "Guess a 4-digit number with no duplicate digits: "); int guess; try{ guess = input.nextInt(); if(hasDupes(guess)) continue; }catch(InputMismatchException e){ continue; } guesses++; String guessStr = guess + ""; for(int i= 0;i < 4;i++){ if(guessStr.charAt(i) == targetStr.charAt(i)){ bulls++; }else if(targetStr.contains(guessStr.charAt(i)+"")){ cows++; } } if(bulls == 4){ guessed = true; }else{ System.out.println(cows+" Cows and "+bulls+" Bulls."); } }while(!guessed); System.out.println("You won after "+guesses+" guesses!"); }
public static boolean hasDupes(int num){ boolean[] digs = new boolean[10]; while(num > 0){ if(digs[num%10]) return true; digs[num%10] = true; num/= 10; } return false; } }</lang> Output:
Guess a 4-digit number with no duplicate digits: 5834 2 Cows and 0 Bulls. Guess a 4-digit number with no duplicate digits: 1234 1 Cows and 0 Bulls. Guess a 4-digit number with no duplicate digits: 4321 1 Cows and 0 Bulls. Guess a 4-digit number with no duplicate digits: 3421 0 Cows and 1 Bulls. Guess a 4-digit number with no duplicate digits: 8412 0 Cows and 0 Bulls. Guess a 4-digit number with no duplicate digits: 3560 1 Cows and 1 Bulls. Guess a 4-digit number with no duplicate digits: 3650 0 Cows and 2 Bulls. Guess a 4-digit number with no duplicate digits: 3759 2 Cows and 2 Bulls. Guess a 4-digit number with no duplicate digits: 3975 2 Cows and 2 Bulls. Guess a 4-digit number with no duplicate digits: 3957 You won after 10 guesses!
Perl
<lang perl>use strict; use Data::Random qw(rand_set);
my $size = 4; my $chosen = join("", rand_set( set => ["1".."9"], size => $size));
print "I've chosen a number from $size unique digits from 1 to 9; you need to input $size unique digits to guess my number\n";
my $guesses = 0; my $guess; while(1) {
$guesses++;
while(1) {
print "\nNext guess [$guesses]: ";
$guess = <STDIN>;
chomp $guess;
if ( !checkguess($guess) ) {
print "$size digits, no repetition, no 0... retry\n";
} else { last; }
}
if ( $guess eq $chosen ) {
print "You did it in $guesses attempts!\n"; last;
} else {
my $bulls=0; my $cows=0; for my $i (0 .. $size-1) { if ( substr($guess, $i, 1) eq substr($chosen, $i, 1) ) { $bulls++; } elsif ( index($chosen, substr($guess, $i, 1)) >= 0 ) { $cows++; } } print "$cows cows, $bulls bulls\n";
}
}
sub checkguess($) {
my $g = shift;
my %h = ();
for my $k ( split(//, $g) ) {
return 0 if exists $h{$k}; $h{$k} = 1;
}
return ( $g =~ /^[1-9]{4}$/ );
}</lang>
Python
<lang python>
Bulls and cows. A game pre-dating, and similar to, Mastermind.
import random
digits = '123456789' size = 4 chosen = .join(random.sample(digits,size))
- print chosen # Debug
print I have chosen a number from %s unique digits from 1 to 9 arranged in a random order. You need to input a %i digit, unique digit number as a guess at what I have chosen % (size, size) guesses = 0 while True:
guesses += 1
while True:
# get a good guess
guess = raw_input('\nNext guess [%i]: ' % guesses).strip()
if len(guess) == 4 and \
all(char in digits for char in guess) \
and len(set(guess)) == size:
break
print "Problem, try again. You need to enter %i unique digits from 1 to 9" % size
if guess == chosen:
print '\nCongratulations you guessed correctly in',guesses,'attempts'
break
bulls = cows = 0
for i in range(size):
if guess[i] == chosen[i]:
bulls += 1
elif guess[i] in chosen:
cows += 1
print ' %i Bulls\n %i Cows' % (bulls, cows)</lang>
Sample output:
I have chosen a number from 4 unique digits from 1 to 9 arranged in a random order. You need to input a 4 digit, unique digit number as a guess at what I have chosen Next guess [1]: 79 Problem, try again. You need to enter 4 unique digits from 1 to 9 Next guess [1]: 7983 2 Bulls 2 Cows Next guess [2]: 7938 Congratulations you guessed correctly in 2 attempts
Smalltalk
<lang smalltalk>Object subclass: BullsCows [
|number|
BullsCows class >> new: secretNum [ |i|
i := self basicNew.
(self isValid: secretNum)
ifFalse: [ SystemExceptions.InvalidArgument
signalOn: secretNum
reason: 'You need 4 unique digits from 1 to 9' ].
i setNumber: secretNum.
^ i
]
BullsCows class >> new [ |b| b := Set new.
[ b size < 4 ]
whileTrue: [ b add: ((Random between: 1 and: 9) displayString first) ].
^ self new: (b asString)
]
BullsCows class >> isValid: num [
^ (num asSet size = 4) & ((num asSet includes: $0) not)
]
setNumber: num [ number := num ]
check: guess [ |bc| bc := Bag new.
1 to: 4 do: [ :i |
(number at: i) = (guess at: i)
ifTrue: [ bc add: 'bulls' ]
ifFalse: [
(number includes: (guess at: i))
ifTrue: [ bc add: 'cows' ]
]
].
^ bc
]
].
'Guess the 4-digits number (digits from 1 to 9, no repetition)' displayNl.
|guessMe d r tries| [
tries := 0.
guessMe := BullsCows new.
[
[
'Write 4 digits: ' display.
d := stdin nextLine.
(BullsCows isValid: d)
] whileFalse: [
'Insert 4 digits, no repetition, exclude the digit 0' displayNl
].
r := guessMe check: d.
tries := tries + 1.
(r occurrencesOf: 'bulls') = 4
] whileFalse: [
('%1 cows, %2 bulls' % { r occurrencesOf: 'cows'. r occurrencesOf: 'bulls' })
displayNl.
].
('Good, you guessed it in %1 tries!' % { tries }) displayNl.
'Do you want to play again? [y/n]' display.
( (stdin nextLine) = 'y' )
] whileTrue: [ Character nl displayNl ].</lang>
Tcl
<lang tcl>proc main {} {
fconfigure stdout -buffering none set length 4 puts "I have chosen a number from $length unique digits from 1 to 9 arranged in a random order.
You need to input a $length digit, unique digit number as a guess at what I have chosen
"
while true {
set word [generateWord $length]
set count 1
while {[set guess [getGuess $length]] ne $word} {
printScore $length $word $guess
incr count
}
puts "You guessed correctly in $count tries."
if {[yn "Play again?"] eq "n"} break
}
}
proc generateWord {length} {
set chars 123456789
for {set i 1} {$i <= $length} {incr i} {
set idx [expr {int(rand() * [string length $chars])}]
append word [string index $chars $idx]
set chars [string replace $chars $idx $idx]
}
return $word
# here's another way to generate word with no duplications
set word ""
while {[string length $word] < $length} {
set char [expr {int(1 + 9*rand())}]
if {[string first $char $word] == -1} {
append word $char
}
}
}
proc getGuess {length} {
puts -nonewline "Enter your guess: "
while true {
gets stdin guess
if {[string match [string repeat {[1-9]} $length] $guess]} {
return $guess
}
if {[string tolower [string trim $guess]] eq "quit"} {
puts Bye
exit
}
puts "The word must be $length digits between 1 and 9 inclusive. Try again."
}
}
proc printScore {length word guess} {
set bulls 0
set cows 0
for {set i 0} {$i < $length} {incr i} {
if {[string index $word $i] eq [string index $guess $i]} {
incr bulls
set word [string replace $word $i $i +]
}
}
puts " $bulls bulls"
for {set i 0} {$i < $length} {incr i} {
if {[set j [string first [string index $guess $i] $word]] != -1} {
incr cows
set word [string replace $word $j $j -]
}
}
puts " $cows cows"
}
proc yn {msg} {
while true {
puts -nonewline "$msg \[y/n] "
gets stdin ans
set char [string tolower [string index [string trim $ans] 0]]
if {$char eq "y" || $char eq "n"} {
return $char
}
}
}
main</lang>