Bulls and cows/Player
From Rosetta Code
You are encouraged to solve this task according to the task description, using any language you may know.
The task is to write a player of the Bulls and Cows game, rather than a scorer. The player should give intermediate answers that respect the scores to previous attempts.
One method is to generate a list of all possible numbers that could be the answer, then to prune the list by keeping only those numbers that would give an equivalent score to how your last guess was scored. Your next guess can be any number from the pruned list.
Either you guess correctly or run out of numbers to guess, which indicates a problem with the scoring.
- Cf,
Contents |
[edit] Ada
bulls_player.adb:
with Ada.Text_IO;
with Ada.Containers.Vectors;
with Ada.Numerics.Discrete_Random;
procedure Bulls_Player is
-- package for In-/Output of natural numbers
package Nat_IO is new Ada.Text_IO.Integer_IO (Natural);
-- for comparing length of the vectors
use type Ada.Containers.Count_Type;
-- number of digits
Guessing_Length : constant := 4;
-- digit has to be from 1 to 9
type Digit is range 1 .. 9;
-- a sequence has specified length of digits
type Sequence is array (1 .. Guessing_Length) of Digit;
-- data structure to store the possible answers
package Sequence_Vectors is new Ada.Containers.Vectors
(Element_Type => Sequence,
Index_Type => Positive);
-- check if sequence contains each digit only once
function Is_Valid (S : Sequence) return Boolean is
Appeared : array (Digit) of Boolean := (others => False);
begin
for I in S'Range loop
if Appeared (S (I)) then
return False;
end if;
Appeared (S (I)) := True;
end loop;
return True;
end Is_Valid;
-- calculate all possible sequences and store them in the vector
procedure Fill_Pool (Pool : in out Sequence_Vectors.Vector) is
Finished : exception;
-- count the sequence up by one
function Next (S : Sequence) return Sequence is
Result : Sequence := S;
Index : Positive := S'Last;
begin
loop
-- overflow at a position causes next position to increase
if Result (Index) = Digit'Last then
Result (Index) := Digit'First;
-- overflow at maximum position
-- we have processed all possible values
if Index = Result'First then
raise Finished;
end if;
Index := Index - 1;
else
Result (Index) := Result (Index) + 1;
return Result;
end if;
end loop;
end Next;
X : Sequence := (others => 1);
begin
loop
-- append all valid values
if Is_Valid (X) then
Pool.Append (X);
end if;
X := Next (X);
end loop;
exception
when Finished =>
-- the exception tells us that we have added all possible values
-- simply return and do nothing.
null;
end Fill_Pool;
-- generate a random index from the pool
function Random_Index (Pool : Sequence_Vectors.Vector) return Positive is
subtype Possible_Indexes is Positive range
Pool.First_Index .. Pool.Last_Index;
package Index_Random is new Ada.Numerics.Discrete_Random
(Possible_Indexes);
Index_Gen : Index_Random.Generator;
begin
Index_Random.Reset (Index_Gen);
return Index_Random.Random (Index_Gen);
end Random_Index;
-- get the answer from the player, simple validity tests
procedure Get_Answer (S : Sequence; Bulls, Cows : out Natural) is
Valid : Boolean := False;
begin
Bulls := 0;
Cows := 0;
while not Valid loop
-- output the sequence
Ada.Text_IO.Put ("How is the score for:");
for I in S'Range loop
Ada.Text_IO.Put (Digit'Image (S (I)));
end loop;
Ada.Text_IO.New_Line;
begin
Ada.Text_IO.Put ("Bulls:");
Nat_IO.Get (Bulls);
Ada.Text_IO.Put ("Cows:");
Nat_IO.Get (Cows);
if Bulls + Cows <= Guessing_Length then
Valid := True;
else
Ada.Text_IO.Put_Line ("Invalid answer, try again.");
end if;
exception
when others =>
null;
end;
end loop;
end Get_Answer;
-- remove all sequences that wouldn't give an equivalent score
procedure Strip
(V : in out Sequence_Vectors.Vector;
S : Sequence;
Bulls, Cows : Natural)
is
function Has_To_Be_Removed (Position : Positive) return Boolean is
Testant : constant Sequence := V.Element (Position);
Bull_Score : Natural := 0;
Cows_Score : Natural := 0;
begin
for I in Testant'Range loop
for J in S'Range loop
if Testant (I) = S (J) then
-- same digit at same position: Bull!
if I = J then
Bull_Score := Bull_Score + 1;
else
Cow_Score := Cow_Score + 1;
end if;
end if;
end loop;
end loop;
return Cow_Score /= Cows or else Bull_Score /= Bulls;
end Has_To_Be_Removed;
begin
for Index in reverse V.First_Index .. V.Last_Index loop
if Has_To_Be_Removed (Index) then
V.Delete (Index);
end if;
end loop;
end Strip;
-- main routine
procedure Solve is
All_Sequences : Sequence_Vectors.Vector;
Test_Index : Positive;
Test_Sequence : Sequence;
Bulls, Cows : Natural;
begin
-- generate all possible sequences
Fill_Pool (All_Sequences);
loop
-- pick at random
Test_Index := Random_Index (All_Sequences);
Test_Sequence := All_Sequences.Element (Test_Index);
-- ask player
Get_Answer (Test_Sequence, Bulls, Cows);
-- hooray, we have it!
exit when Bulls = 4;
All_Sequences.Delete (Test_Index);
Strip (All_Sequences, Test_Sequence, Bulls, Cows);
exit when All_Sequences.Length <= 1;
end loop;
if All_Sequences.Length = 0 then
-- oops, shouldn't happen
Ada.Text_IO.Put_Line
("I give up, there has to be a bug in" &
"your scoring or in my algorithm.");
else
if All_Sequences.Length = 1 then
Ada.Text_IO.Put ("The sequence you thought has to be:");
Test_Sequence := All_Sequences.First_Element;
else
Ada.Text_IO.Put ("The sequence you thought of was:");
end if;
for I in Test_Sequence'Range loop
Ada.Text_IO.Put (Digit'Image (Test_Sequence (I)));
end loop;
end if;
end Solve;
begin
-- output blah blah
Ada.Text_IO.Put_Line ("Bulls and Cows, Your turn!");
Ada.Text_IO.New_Line;
Ada.Text_IO.Put_Line
("Think of a sequence of" &
Integer'Image (Guessing_Length) &
" different digits.");
Ada.Text_IO.Put_Line ("I will try to guess it. For each correctly placed");
Ada.Text_IO.Put_Line ("digit I score 1 Bull. For each digit that is on");
Ada.Text_IO.Put_Line ("the wrong place I score 1 Cow. After each guess");
Ada.Text_IO.Put_Line ("you tell me my score.");
Ada.Text_IO.New_Line;
Ada.Text_IO.Put_Line ("Let's start.");
Ada.Text_IO.New_Line;
-- solve the puzzle
Solve;
end Bulls_Player;
output:
Bulls and Cows, Your turn! Think of a sequence of 4 different digits. I will try to guess it. For each correctly placed digit I score 1 Bull. For each digit that is on the wrong place I score 1 Cow. After each guess you tell me my score. Let's start. How is the score for: 8 1 7 5 Bulls:2 Cows:0 How is the score for: 4 1 6 5 Bulls:1 Cows:0 How is the score for: 3 9 7 5 Bulls:1 Cows:2 How is the score for: 9 1 7 3 Bulls:0 Cows:2 The sequence you thought has to be: 8 3 9 5
[edit] BBC BASIC
secret$ = ""
REPEAT
c$ = CHR$(&30 + RND(9))
IF INSTR(secret$, c$) = 0 secret$ += c$
UNTIL LEN(secret$) = 4
FOR i% = 1234 TO 9876
possible$ += STR$(i%)
NEXT
PRINT "Guess a four-digit number with no digit used twice."
guesses% = 0
REPEAT
IF LEN(possible$) = 4 THEN
guess$ = possible$
ELSE
guess$ = MID$(possible$, 4*RND(LEN(possible$) / 4) - 3, 4)
ENDIF
PRINT '"Computer guesses " guess$
guesses% += 1
IF guess$ = secret$ PRINT "Correctly guessed after "; guesses% " guesses!" : END
PROCcount(secret$, guess$, bulls%, cows%)
PRINT "giving " ;bulls% " bull(s) and " ;cows% " cow(s)."
i% = 1
REPEAT
temp$ = MID$(possible$, i%, 4)
PROCcount(temp$, guess$, testbulls%, testcows%)
IF bulls%=testbulls% IF cows%=testcows% THEN
i% += 4
ELSE
possible$ = LEFT$(possible$, i%-1) + MID$(possible$, i%+4)
ENDIF
UNTIL i% > LEN(possible$)
IF INSTR(possible$, secret$) = 0 STOP
UNTIL FALSE
END
DEF PROCcount(secret$, guess$, RETURN bulls%, RETURN cows%)
LOCAL i%, c$
bulls% = 0
cows% = 0
FOR i% = 1 TO 4
c$ = MID$(secret$, i%, 1)
IF MID$(guess$, i%, 1) = c$ THEN
bulls% += 1
ELSE IF INSTR(guess$, c$) THEN
cows% += 1
ENDIF
ENDIF
NEXT i%
ENDPROC
[edit] C
#include <stdio.h>sample output for 4 digits:
#include <stdlib.h>
#include <string.h>
#include <time.h>
char *list;
const char *line = "--------+--------------------\n";
int len = 0;
int irand(int n)
{
int r, rand_max = RAND_MAX - (RAND_MAX % n);
do { r = rand(); } while(r >= rand_max);
return r / (rand_max / n);
}
char* get_digits(int n, char *ret)
{
int i, j;
char d[] = "123456789";
for (i = 0; i < n; i++) {
j = irand(9 - i);
ret[i] = d[i + j];
if (j) d[i + j] = d[i], d[i] = ret[i];
}
return ret;
}
#define MASK(x) (1 << (x - '1'))
int score(const char *digits, const char *guess, int *cow)
{
int i, bits = 0, bull = *cow = 0;
for (i = 0; guess[i] != '\0'; i++)
if (guess[i] != digits[i])
bits |= MASK(digits[i]);
else ++bull;
while (i--) *cow += ((bits & MASK(guess[i])) != 0);
return bull;
}
void pick(int n, int got, int marker, char *buf)
{
int i, bits = 1;
if (got >= n)
strcpy(list + (n + 1) * len++, buf);
else
for (i = 0; i < 9; i++, bits *= 2) {
if ((marker & bits)) continue;
buf[got] = i + '1';
pick(n, got + 1, marker | bits, buf);
}
}
void filter(const char *buf, int n, int bull, int cow)
{
int i = 0, c;
char *ptr = list;
while (i < len) {
if (score(ptr, buf, &c) != bull || c != cow)
strcpy(ptr, list + --len * (n + 1));
else
ptr += n + 1, i++;
}
}
void game(const char *tgt, char *buf)
{
int i, p, bull, cow, n = strlen(tgt);
for (i = 0, p = 1; i < n && (p *= 9 - i); i++);
list = malloc(p * (n + 1));
pick(n, 0, 0, buf);
for (p = 1, bull = 0; n - bull; p++) {
strcpy(buf, list + (n + 1) * irand(len));
bull = score(tgt, buf, &cow);
printf("Guess %2d| %s (from: %d)\n"
"Score | %d bull, %d cow\n%s",
p, buf, len, bull, cow, line);
filter(buf, n, bull, cow);
}
}
int main(int c, char **v)
{
int n = c > 1 ? atoi(v[1]) : 4;
char secret[10] = "", answer[10] = "";
srand(time(0));
printf("%sSecret | %s\n%s", line, get_digits(n, secret), line);
game(secret, answer);
return 0;
}
--------+--------------------sample output for 9 digits
Secret | 5437
--------+--------------------
Guess 1| 7198 (from: 3024)
Score | 0 bull, 1 cow
--------+--------------------
Guess 2| 2386 (from: 720)
Score | 0 bull, 1 cow
--------+--------------------
Guess 3| 5743 (from: 122)
Score | 1 bull, 3 cow
--------+--------------------
Guess 4| 5437 (from: 5)
Score | 4 bull, 0 cow
--------+--------------------
--------+--------------------
Secret | 758214936
--------+--------------------
Guess 1| 245863197 (from: 362880)
Score | 0 bull, 9 cow
--------+--------------------
Guess 2| 964715382 (from: 133496)
Score | 1 bull, 8 cow
--------+--------------------
Guess 3| 614927853 (from: 48722)
Score | 0 bull, 9 cow
--------+--------------------
Guess 4| 567391248 (from: 15926)
Score | 0 bull, 9 cow
--------+--------------------
Guess 5| 839174562 (from: 4473)
Score | 1 bull, 8 cow
--------+--------------------
Guess 6| 489635721 (from: 1503)
Score | 0 bull, 9 cow
--------+--------------------
Guess 7| 723156984 (from: 317)
Score | 2 bull, 7 cow
--------+--------------------
Guess 8| 953278614 (from: 89)
Score | 2 bull, 7 cow
--------+--------------------
Guess 9| 321479685 (from: 24)
Score | 0 bull, 9 cow
--------+--------------------
Guess 10| 893752416 (from: 4)
Score | 1 bull, 8 cow
--------+--------------------
Guess 11| 758214936 (from: 1)
Score | 9 bull, 0 cow
--------+--------------------
[edit] C++
#include <iostream>
#include <sstream>
#include <iomanip>
#include <algorithm>
#include <vector>
#include <time.h>
//--------------------------------------------------------------------------------------------------
using namespace std;
//--------------------------------------------------------------------------------------------------
const unsigned int LEN = 4;
//--------------------------------------------------------------------------------------------------
class CowsAndBulls_Player
{
public:
CowsAndBulls_Player() { fillPool(); }
void play() { secret = createSecret(); guess(); }
private:
void guess()
{
pair<int, int> res; int cc = 1;
cout << endl << " SECRET: " << secret << endl << "==============" << endl;
cout << "+-----------+---------+--------+\n| GUESS | BULLS | COWS |\n+-----------+---------+--------+\n";
while( true )
{
string gs = gimmeANumber();
if( gs.empty() ) { cout << endl << "Something went wrong with the scoring..." << endl << "Cannot find an answer!" << endl; return; }
if( scoreIt( gs, res ) ) { cout << endl << "I found the secret number!" << endl << "It is: " << gs << endl; return; }
cout << "| " << gs << " | " << setw( 3 ) << res.first << " | " << setw( 3 ) << res.second << " |\n+-----------+---------+--------+\n";
clearPool( gs, res );
}
}
void clearPool( string gs, pair<int, int>& r )
{
vector<string>::iterator pi = pool.begin();
while( pi != pool.end() )
{
if( removeIt( gs, ( *pi ), r ) ) pi = pool.erase( pi );
else pi++;
}
}
string gimmeANumber()
{
if( pool.empty() ) return "";
return pool[rand() % pool.size()];
}
void fillPool()
{
for( int x = 1234; x < 9877; x++ )
{
ostringstream oss; oss << x;
if( check( oss.str() ) ) pool.push_back( oss.str() );
}
}
bool check( string s )
{
for( string::iterator si = s.begin(); si != s.end(); si++ )
{
if( ( *si ) == '0' ) return false;
if( count( s.begin(), s.end(), ( *si ) ) > 1 ) return false;
}
return true;
}
bool removeIt( string gs, string ts, pair<int, int>& res )
{
pair<int, int> tp; getScore( gs, ts, tp );
return tp != res;
}
bool scoreIt( string gs, pair<int, int>& res )
{
getScore( gs, secret, res );
return res.first == LEN;
}
void getScore( string gs, string st, pair<int, int>& pr )
{
pr.first = pr.second = 0;
for( unsigned int ui = 0; ui < LEN; ui++ )
{
if( gs[ui] == st[ui] ) pr.first++;
else
{
for( unsigned int vi = 0; vi < LEN; vi++ )
if( gs[ui] == st[vi] ) pr.second++;
}
}
}
string createSecret()
{
string n = "123456789", rs = "";
while( rs.length() < LEN )
{
int r = rand() % n.length();
rs += n[r]; n.erase( r, 1 );
}
return rs;
}
string secret;
vector<string> pool;
};
//--------------------------------------------------------------------------------------------------
int main( int argc, char* argv[] )
{
srand( static_cast<unsigned int>( time( NULL ) ) ); CowsAndBulls_Player cb;
cb.play(); cout << endl << endl;
return system( "pause" );
}
//--------------------------------------------------------------------------------------------------
Output:
SECRET: 6281 ============== +-----------+---------+--------+ | GUESS | BULLS | COWS | +-----------+---------+--------+ | 5132 | 0 | 2 | +-----------+---------+--------+ | 1568 | 0 | 3 | +-----------+---------+--------+ | 2685 | 1 | 2 | +-----------+---------+--------+ | 2816 | 0 | 4 | +-----------+---------+--------+ I found the secret number! It is: 6281
[edit] C#
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace BullsAndCows
{
class Program
{
const int ANSWER_SIZE = 4;
static IEnumerable<string> Permutations(int size)
{
if (size > 0)
{
foreach (string s in Permutations(size - 1))
foreach (char n in "123456789")
if (!s.Contains(n))
yield return s + n;
}
else
yield return "";
}
static IEnumerable<T> Shuffle<T>(IEnumerable<T> source)
{
Random random = new Random();
List<T> list = source.ToList();
while (list.Count > 0)
{
int ix = random.Next(list.Count);
yield return list[ix];
list.RemoveAt(ix);
}
}
static bool ReadBullsCows(out int bulls, out int cows)
{
string[] input = Console.ReadLine().Split(',').ToArray();
bulls = cows = 0;
if (input.Length < 2)
return false;
else
return int.TryParse(input[0], out bulls)
&& int.TryParse(input[1], out cows);
}
static void Main(string[] args)
{
Console.WriteLine("Bulls and Cows");
Console.WriteLine("==============");
Console.WriteLine();
List<string> answers = Shuffle(Permutations(ANSWER_SIZE)).ToList();
while (answers.Count > 1)
{
string guess = answers[0];
Console.Write("My guess is {0}. How many bulls, cows? ", guess);
int bulls, cows;
if (!ReadBullsCows(out bulls, out cows))
Console.WriteLine("Sorry, I didn't understand that. Please try again.");
else
for (int ans = answers.Count - 1; ans >= 0; ans--)
{
int tb = 0, tc = 0;
for (int ix = 0; ix < ANSWER_SIZE; ix++)
if (answers[ans][ix] == guess[ix])
tb++;
else if (answers[ans].Contains(guess[ix]))
tc++;
if ((tb != bulls) || (tc != cows))
answers.RemoveAt(ans);
}
}
if (answers.Count == 1)
Console.WriteLine("Hooray! The answer is {0}!", answers[0]);
else
Console.WriteLine("No possible answer fits the scores you gave.");
}
}
}
Example output:-
Bulls and Cows ============== My guess is 7854. How many bulls, cows? 0,1 My guess is 1539. How many bulls, cows? 1,2 My guess is 2935. How many bulls, cows? 2,1 My guess is 9635. How many bulls, cows? 1,3 Hooray! The answer is 5936!
[edit] D
import std.stdio, std.random, std.algorithm, std.range, std.ascii;
auto scoreCalc(in dchar[] guess, in dchar[] chosen) {
immutable bulls = guess.zip(chosen).count!q{ a[0] == a[1] };
immutable cows = count!(p => p[0] != p[1] && chosen.canFind(p[0]))
(zip(guess, chosen));
return [bulls, cows];
}
void main() {
auto d9 = "123456789"d.dup;
auto choices = cartesianProduct(d9, d9, d9, d9)
.map!(t => [t[]])
.filter!(a => a.sort().uniq.walkLength == 4)
.array;
choices.randomShuffle;
do {
const ans = choices[0];
writef("My guess is %s. How many bulls and cows? ", ans);
const score = readln.filter!isDigit.map!q{ a-'0' }.array;
choices = choices.filter!(c => scoreCalc(c, ans) == score).array;
if (choices.empty)
return writeln("Nothing fits the scores you gave.");
} while (choices.length > 1);
writeln("Solution found: ", choices[0]);
}
- Example output:
My guess is 9345. How many bulls and cows? 02 My guess is 8496. How many bulls and cows? 01 My guess is 2739. How many bulls and cows? 12 My guess is 3129. How many bulls and cows? 03 My guess is 7931. How many bulls and cows? 40 Solution found: 7931
[edit] Euphoria
include std/sequence.e
constant line = "--------+--------------------\n"
constant digits = "123456789"
sequence list = {}
function get_digits(integer n)
integer j
sequence d = digits, ret = ""
for i=1 to n do
j = rand(length(digits)-i)
ret &= d[i+j]
if j then
d[i+j] = d[i]
d[i] = ret[i]
end if
end for
return ret
end function
function MASK(integer x)
return power(2,x-digits[1])
end function
function score(sequence pattern, sequence guess)
integer bits = 0, bull = 0, cow = 0
for i = 1 to length(guess) do
if guess[i] != pattern[i] then
bits += MASK(pattern[i])
else
bull += 1
end if
end for
for i = 1 to length(guess) do
cow += and_bits(bits,MASK(guess[i])) != 0
end for
return {bull, cow}
end function
procedure pick(integer n, integer got, integer marker, sequence buf)
integer bits = 1
if got >= n then
list = append(list,buf)
else
for i = 0 to length(digits)-1 do
if not and_bits(marker,bits) then
buf[got+1] = i+digits[1]
pick(n, got+1, or_bits(marker,bits), buf)
end if
bits *= 2
end for
end if
end procedure
function tester(sequence item, sequence data)
return equal(score(item,data[1]),data[2])
end function
constant tester_id = routine_id("tester")
procedure game(sequence tgt)
integer p, n = length(tgt)
sequence buf = repeat(0,n), bc
list = {}
pick(n,0,0,buf)
p = 1
bc = {0,0}
while bc[1]<n do
buf = list[rand($)]
bc = score(tgt,buf)
printf(1,"Guess %2d| %s (from: %d)\nScore | %d bull, %d cow\n%s",
{p, buf, length(list)} & bc & {line})
list = filter(list, tester_id, {buf, bc})
p+=1
end while
end procedure
constant n = 4
sequence secret = get_digits(n)
printf(1,"%sSecret | %s\n%s", {line, secret, line})
game(secret)
Output:
--------+-------------------- Secret | 6478 --------+-------------------- Guess 1| 5813 (from: 3024) Score | 0 bull, 1 cow --------+-------------------- Guess 2| 6782 (from: 720) Score | 1 bull, 2 cow --------+-------------------- Guess 3| 2689 (from: 62) Score | 0 bull, 2 cow --------+-------------------- Guess 4| 7562 (from: 19) Score | 0 bull, 2 cow --------+-------------------- Guess 5| 6478 (from: 4) Score | 4 bull, 0 cow --------+--------------------
[edit] Fortran
module Player
implicit none
contains
subroutine Init(candidates)
integer, intent(in out) :: candidates(:)
integer :: a, b, c, d, n
n = 0
thousands: do a = 1, 9
hundreds: do b = 1, 9
tens: do c = 1, 9
units: do d = 1, 9
if (b == a) cycle hundreds
if (c == b .or. c == a) cycle tens
if (d == c .or. d == b .or. d == a) cycle units
n = n + 1
candidates(n) = a*1000 + b*100 + c*10 + d
end do units
end do tens
end do hundreds
end do thousands
end subroutine init
subroutine Evaluate(bulls, cows, guess, candidates)
integer, intent(in) :: bulls, cows, guess
integer, intent(in out) :: candidates(:)
integer :: b, c, s, i, j
character(4) :: n1, n2
write(n1, "(i4)") guess
do i = 1, size(candidates)
if (candidates(i) == 0) cycle
b = 0
c = 0
write(n2, "(i4)") candidates(i)
do j = 1, 4
s = index(n1, n2(j:j))
if(s /= 0) then
if(s == j) then
b = b + 1
else
c = c + 1
end if
end if
end do
if(.not.(b == bulls .and. c == cows)) candidates(i) = 0
end do
end subroutine Evaluate
function Nextguess(candidates)
integer :: Nextguess
integer, intent(in out) :: candidates(:)
integer :: i
nextguess = 0
do i = 1, size(candidates)
if(candidates(i) /= 0) then
nextguess = candidates(i)
candidates(i) = 0
return
end if
end do
end function
end module Player
program Bulls_Cows
use Player
implicit none
integer :: bulls, cows, initial, guess
integer :: candidates(3024) = 0
real :: rnum
! Fill candidates array with all possible number combinations
call Init(candidates)
! Random initial guess
call random_seed
call random_number(rnum)
initial = 3024 * rnum + 1
guess = candidates(initial)
candidates(initial) = 0
do
write(*, "(a, i4)") "My guess is ", guess
write(*, "(a)", advance = "no") "Please score number of Bulls and Cows: "
read*, bulls, cows
write(*,*)
if (bulls == 4) then
write(*, "(a)") "Solved!"
exit
end if
! We haven't found the solution yet so evaluate the remaining candidates
! and eliminate those that do not match the previous score given
call Evaluate(bulls, cows, guess, candidates)
! Get the next guess from the candidates that are left
guess = Nextguess(candidates)
if(guess == 0) then
! If we get here then no solution is achievable from the scores given or the program is bugged
write(*, "(a)") "Sorry! I can't find a solution. Possible mistake in the scoring"
exit
end if
end do
end program
Output
My guess is 1528 Please score number of Bulls and Cows: 0 1 My guess is 2346 Please score number of Bulls and Cows: 0 1 My guess is 3179 Please score number of Bulls and Cows: 1 2 My guess is 3795 Please score number of Bulls and Cows: 0 2 My guess is 4971 Please score number of Bulls and Cows: 2 2 My guess is 9471 Please score number of Bulls and Cows: 4 0 Solved!
[edit] Go
Notes: Strategy per the suggestion in the problem description. Check algorithm lifted from Bulls and cows program. Code here uses Go's built in map type as the container for the list of still-possible numbers; only the map key is used, the value is assigned a dummy of 0.
package main
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
)
func main() {
fmt.Println(`Cows and bulls/player
You think of four digit number of unique digits in the range 1 to 9.
I guess. You score my guess:
A correct digit but not in the correct place is a cow.
A correct digit in the correct place is a bull.
You give my score as two numbers separated with a space.`)
// generate possible patterns, store in map
m := make(map[string]int)
var g func([]byte, int)
g = func(digits []byte, fixed int) {
if fixed == 4 {
m[string(digits[:4])] = 0
return
}
for i := fixed; i < len(digits); i++ {
digits[fixed], digits[i] = digits[i], digits[fixed]
g(digits, fixed+1)
digits[fixed], digits[i] = digits[i], digits[fixed]
}
}
g([]byte("123456789"), 0)
// guess/score/eliminate loop
for in := bufio.NewReader(os.Stdin);; {
// pick a value, ie, guess
var guess string
for guess = range m {
delete(m, guess)
break
}
// get and parse score
var c, b uint
for ;; fmt.Println("Score guess as two numbers: cows bulls") {
fmt.Printf("My guess: %s. Score? (c b) ", guess)
score, err := in.ReadString('\n')
if err != nil {
fmt.Println("\nSo, bye.")
return
}
s2 := strings.Fields(score)
if len(s2) == 2 {
c2, err := strconv.ParseUint(s2[0], 10, 0)
if err == nil && c2 <= 4 {
b2, err := strconv.ParseUint(s2[1], 10, 0)
if err == nil && c2+b2 <= 4 {
c = uint(c2)
b = uint(b2)
break
}
}
}
}
// check for win
if b == 4 {
fmt.Println("I did it. :)")
return
}
// eliminate patterns with non-matching scores
for pat := range m {
var cows, bulls uint
for ig, cg := range guess {
switch strings.IndexRune(pat, cg) {
case -1:
default: // I just think cows should go first
cows++
case ig:
bulls++
}
}
if cows != c || bulls != b {
delete(m, pat)
}
}
// check for inconsistency
if len(m) == 0 {
fmt.Println("Oops, check scoring.")
return
}
}
}
[edit] Haskell
import Data.List
import Control.Monad
import System.Random (randomRIO)
import Data.Char(digitToInt)
combinationsOf 0 _ = [[]]
combinationsOf _ [] = []
combinationsOf k (x:xs) = map (x:) (combinationsOf (k-1) xs) ++ combinationsOf k xs
player = do
let ps = concatMap permutations $ combinationsOf 4 ['1'..'9']
play ps where
play ps =
if null ps then
putStrLn "Unable to find a solution"
else do i <- randomRIO(0,length ps - 1)
let p = ps!!i :: String
putStrLn ("My guess is " ++ p) >> putStrLn "How many bulls and cows?"
input <- takeInput
let bc = input ::[Int]
ps' = filter((==sum bc).length. filter id. map (flip elem p))
$ filter((==head bc).length. filter id. zipWith (==) p) ps
if length ps' == 1 then putStrLn $ "The answer is " ++ head ps'
else play ps'
takeInput = do
inp <- getLine
let ui = map digitToInt $ take 2 $ filter(`elem` ['0'..'4']) inp
if sum ui > 4 || length ui /= 2 then
do putStrLn "Wrong input. Try again"
takeInput
else return ui
Example:
*Main> player
My guess is 4923
How many bulls and cows?
2 2
My guess is 3924
How many bulls and cows?
1 3
My guess is 4329
How many bulls and cows?
1 3
My guess is 4932
How many bulls and cows?
4 0
The answer is 4932
[edit] J
require'misc'
poss=:1+~.4{."1 (i.!9)A.i.9
fmt=: ' ' -.~ ":
play=:3 :0
while.1<#poss=.poss do.
smoutput'guessing ',fmt guess=.({~ ?@#)poss
bc=.+/\_".prompt 'how many bull and cows? '
poss=.poss #~({.bc)=guess+/@:="1 poss
poss=.poss #~({:bc)=guess+/@e."1 poss
end.
if.#poss do.
'the answer is ',fmt,poss
else.
'no valid possibilities'
end.
)
For example:
play''
guessing 7461
how many bull and cows? 0 1
guessing 3215
how many bull and cows? 0 3
guessing 2357
how many bull and cows? 2 0
guessing 1359
how many bull and cows? 3 0
the answer is 1358
[edit] Liberty BASIC
As supplied rhe code shows the remaining pool of numbers after each guess is scored.
guesses =0
do while len( secret$) <4 ' zero not allowed <<<<<<<<<
n$ =chr$( int( rnd( 1) *9) +49)
if not( instr( secret$, n$)) then secret$ =secret$ +n$
loop
print " Secretly, my opponent just chose a number. But she didn't tell anyone! "; secret$; "."
print " I can however be given a score for my guesses."
for i =1234 to 9876 ' <<<<<<<<<
if check( str$( i)) =0 then available$ =available$ +" " +str$( i): k =k +1
next i
available$ =trim$( available$) ' remove the surplus, leading space
print "Currently holding "; k; " possible numbers. "
while 1
guess$ =word$( available$, 1 +int( k *rnd( 1)), " ")
print "Computer guessed "; guess$; " & got ";
bulls =0
cows =0
guesses =guesses +1
r$ =score$( guess$, secret$)
bulls =val( word$( r$, 1, ","))
cows =val( word$( r$, 2, ","))
print bulls; " bull(s), and "; cows; " cow(s), .... ";
if guess$ =secret$ then
print "Computer won after "; guesses; " guesses!";
secs =( time$( "seconds") -now +86400) mod 86400
print " That took "; secs; " seconds. ENDED!"
print " Now scroll right to see original choice and check!"
exit while
end if
print " so possible numbers are now only..."
kk =0
new$ =""
for j =1 to k
bullsT =0
cowsT =0
possible$ =word$( available$, j, " ")
r$ =score$( guess$, possible$)
bullsT =val( word$( r$, 1, ","))
cowsT =val( word$( r$, 2, ","))
if ( bullsT =bulls) and ( cowsT =cows) then
new$ =new$ +" " +possible$ ' keep those with same score
kk =kk +1
print possible$; " ";
if ( kk mod 20) =0 then print
end if
scan
next j
available$ =trim$( new$)
k =kk
scan
wend
end
function score$( a$, b$) ' return as a csv string the number of bulls & cows.
bulls = 0: cows = 0
for i = 1 to 4
c$ = mid$( a$, i, 1)
if mid$( b$, i, 1) = c$ then
bulls = bulls + 1
else
if instr( b$, c$) <>0 and instr( b$, c$) <>i then cows = cows + 1
end if
next i
score$ =str$( bulls); ","; str$( cows)
end function
function check( i$)
check =0 ' zero flags available: 1 means not available
for i =1 to 3
for j =i +1 to 4
if mid$( i$, i, 1) =mid$( i$, j, 1) then check =1
next j
next i
if instr( i$, "0") then check =1
end function
[edit] Mathematica
bullCow={Count[#1-#2,0],Length[#1\[Intersection]#2]-Count[#1-#2,0]}&;
Module[{r,input,candidates=Permutations[Range[9],{4}]},
While[True,
r=InputString[];
If[r===$Canceled,Break[],
input=ToExpression/@StringSplit@r;
If[Length@input!=3,Print["Input the guess, number of bulls, number of cows, delimited by space."],
candidates=Select[candidates,bullCow[ToCharacterCode@StringJoin[ToString/@#],ToCharacterCode@ToString@input[[1]]]==input[[2;;3]]&];
candidates=SortBy[candidates,{-3,-1}.bullCow[ToCharacterCode@StringJoin[ToString/@#],ToCharacterCode@ToString@input[[1]]]&];
If[candidates==={},Print["No more candidates."];Break[]];
If[Length@candidates==1,Print["Must be: "<>StringJoin[ToString/@candidates[[1]]]];Break[]];
Print[ToString@Length@candidates<>" candidates remaining."];
Print["Can try "<>StringJoin[ToString/@First@candidates]<>"."];
]]]]
Output:
120 candidates remaining. Can try 1256. 36 candidates remaining. Can try 1537. 5 candidates remaining. Can try 1584. Must be: 1639
[edit] Perl
#!/usr/bin/perl
use warnings;
use strict;
use v5.10;
# Build a list of all possible solutions. The regular expression weeds
# out numbers containing zeroes or repeated digits. See how Perl
# automatically converts numbers to strings for us, just because we
# use them as if they were strings:
my @candidates = grep {not /0 | (\d) .* \1 /x} 1234 .. 9876;
# Repeatedly prompt for input until the user supplies a reasonable score.
# The regex validates the user's input and then returns two numbers,
# $+{BULLS} and $+{COWS}.
sub read_score($) {
(my $guess) = @_;
for (;;) {
say "My guess: $guess (from ", 0+@candidates, " possibilities)";
if (<> =~ / ^ \h* (?<BULLS> \d) \h* (?<COWS> \d) \h* $ /x and
$+{BULLS} + $+{COWS} <= 4) {
return ($+{BULLS}, $+{COWS});
}
say "Please specify the number of bulls and the number of cows";
}
}
sub score_correct($$$$) {
my ($a, $b, $bulls, $cows) = @_;
# Count the positions at which the digits match:
my $exact = () = grep {substr($a, $_, 1) eq substr($b, $_, 1)} 0 .. 3;
# Cross-match all digits in $a against all digits in $b, using a regex
# (specifically, a character class) instead of an explicit loop:
my $loose = () = $a =~ /[$b]/g;
return $bulls == $exact && $cows == $loose - $exact;
}
do {
# Pick a number, display it, get the score, and discard candidates
# that don't match the score:
my $guess = @candidates[rand @candidates];
my ($bulls, $cows) = read_score $guess;
@candidates = grep {score_correct $_, $guess, $bulls, $cows} @candidates;
} while (@candidates > 1);
say(@candidates?
"Your secret number is @candidates":
"I think you made a mistake with your scoring");
Sample game:
msl@64Lucid:~/perl$ ./bulls-and-cows
My guess: 1869 (from 3024 possibilities)
1 0
My guess: 3265 (from 240 possibilities)
0 2
My guess: 7853 (from 66 possibilities)
1 2
My guess: 7539 (from 7 possibilities)
0 3
Your secret number is 1357
msl@64Lucid:~/perl$
[edit] Perl 6
# we use the [] reduction meta operator along with the Cartesian Product
# operator X to create the Cartesian Product of four times [1..9] and then get
# all the elements where the number of unique digits is four.
my @candidates = ([X] [1..9] xx 4).tree.grep: *.uniq == 4;
repeat {
my $guess = @candidates.pick;
my ($bulls, $cows) = read-score;
@candidates .= grep: &score-correct;
# note how we declare our two subroutines within the repeat block. This
# limits the scope in which the routines are known to the scope in which
# they are needed and saves us a lot of arguments to our two routines.
sub score-correct($a) {
# use the Z (zip) meta operator along with == to construct the
# list ($a[0] == $b[0], $a[1] == $b[1], ...) and then add it up
# using the reduction meta operator [] and +.
my $exact = [+] $a Z== $guess;
# number of elements of $a that match any element of $b
my $loose = +$a.grep: any @$guess;
return $bulls == $exact && $cows == $loose - $exact;
}
sub read-score() {
loop {
my $score = prompt "My guess: {$guess.join}.\n";
# use the :s modifier to tell Perl 6 to handle spaces
# automatically and save the first digit in $<bulls> and
# the second digit in $<cows>
if $score ~~ m:s/^ $<bulls>=(\d) $<cows>=(\d) $/
and $<bulls> + $<cows> <= 4 {
return +$<bulls>, +$<cows>;
}
say "Please specify the number of bulls and cows";
}
}
} while @candidates > 1;
say @candidates
?? "Your secret number is {@candidates[0].join}!"
!! "I think you made a mistake with your scoring.";
[edit] PicoLisp
(load "@lib/simul.l")
(de bullsAndCows ()
(let Choices (shuffle (mapcan permute (subsets 4 (range 1 9))))
(use (Guess Bulls Cows)
(loop
(prinl "Guessing " (setq Guess (pop 'Choices)))
(prin "How many bulls and cows? ")
(setq Bulls (read) Cows (read))
(setq Choices
(filter
'((C)
(let B (cnt = Guess C)
(and
(= Bulls B)
(= Cows (- (length (sect Guess C)) B)) ) ) )
Choices ) )
(NIL Choices "No matching solution")
(NIL (cdr Choices) (pack "The answer is " (car Choices))) ) ) ) )
Output:
: (bullsAndCows) Guessing 4217 How many bulls and cows? 0 2 Guessing 5762 How many bulls and cows? 1 1 Guessing 9372 How many bulls and cows? 0 1 Guessing 7864 How many bulls and cows? 1 2 Guessing 8754 How many bulls and cows? 0 2 -> "The answer is 2468"
[edit] Prolog
Works with SWI-Prolog. Use of library clfd written by Markus Triska.
There is no algorithm. We explain to Prolog the constraints on the numbers according to the previous guesses and we let Prolog decides of the next guess.
The IA :
:- module('ia.pl', [tirage/1]).
:- use_module(library(clpfd)).
% to store the previous guesses and the answers
:- dynamic guess/2.
% parameters of the engine
% length of the guess
proposition(4).
% Numbers of digits
% 0 -> 8
digits(8).
% tirage(-)
tirage(Ms) :-
% are there previous guesses ?
( bagof([P, R], guess(P,R), Propositions)
-> tirage(Propositions, Ms)
; % First try
tirage_1(Ms)),
!.
% tirage_1(-)
% We choose the first Len numbers
tirage_1(L):-
proposition(Len),
Max is Len-1,
numlist(0, Max, L).
% tirage(+,-)
tirage(L, Ms) :-
proposition(Len),
length(Ms, Len),
digits(Digits),
% The guess continas only this numbers
Ms ins 0..Digits,
all_different(Ms),
% post the constraints
maplist(placees(Ms), L),
% compute a possible solution
label(Ms).
% placees(+, +])
placees(Sol, [Prop, [BP, MP]]) :-
V #= 0,
% compute the numbers of digits in good places
compte_bien_placees(Sol, Prop, V, BP1),
BP1 #= BP,
% compute the numbers of digits inbad places
compte_mal_placees(Sol, Prop, 0, V, MP1),
MP1 #= MP.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% compte_mal_placees(+, +, +, +, -).
% @arg1 : guess to create
% @arg2 : guess already used
% @arg3 : range of the first digit of the previuos arg
% @arg4 : current counter of the digit in bad places
% @arg5 : final counter of the digit in bad places
%
%
compte_mal_placees(_, [], _, MP, MP).
compte_mal_placees(Sol, [H | T], N, MPC, MPF) :-
compte_une_mal_placee(H, N, Sol, 0, 0, VF),
MPC1 #= MPC + VF,
N1 is N+1,
compte_mal_placees(Sol, T, N1, MPC1, MPF).
% Here we check one digit of an already done guess
% compte_une_mal_placee(+, +, +, +, -).
% @arg1 : the digit
% @arg2 : range of this digit
% @arg3 : guess to create
% we check each digit of this guess
% @arg4 : range of the digit of this guess
% @arg5 : current counter of the digit in bad places
% @arg6 : final counter of the digit in bad places
%
compte_une_mal_placee(_H, _N, [], _, TT, TT).
% digit in the same range, continue
compte_une_mal_placee(H, NH, [_H1 | T], NH, TTC, TTF) :-
NH1 is NH + 1, !,
compte_une_mal_placee(H, NH, T, NH1, TTC, TTF).
% same digit in different places
% increment the counter and continue continue
compte_une_mal_placee(H, NH, [H1 | T], NH1, TTC, TTF) :-
H #= H1,
NH \= NH1,
NH2 is NH1 + 1,
TTC1 #= TTC + 1,
compte_une_mal_placee(H, NH, T, NH2, TTC1, TTF).
compte_une_mal_placee(H, NH, [H1 | T], NH1, TTC, TTF) :-
H #\= H1,
NH2 is NH1 + 1,
compte_une_mal_placee(H, NH, T, NH2, TTC, TTF).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% compte_bien_placees(+, +, +, -)
% @arg1 : guess to create
% @arg2 : previous guess
% @arg3 : current counter of the digit in good places
% @arg4 : final counter of the digit in good places
%
%
compte_bien_placees([], [], MP, MP).
compte_bien_placees([H | T], [H1 | T1], MPC, MPF) :-
H #= H1,
MPC1 #= MPC + 1,
compte_bien_placees(T, T1, MPC1, MPF).
compte_bien_placees([H | T], [H1 | T1], MPC, MPF) :-
H #\= H1,
compte_bien_placees(T, T1, MPC, MPF).
The code to play :
bulls_and_cows :-
retractall('ia.pl':guess(_,_)),
retractall(coups(_)),
assert(coups(1)),
repeat,
( tirage(Ms)
-> maplist(add_1, Ms, Ms1),
atomic_list_concat(Ms1, Guess),
retract(coups(Coup)),
Coup_1 is Coup + 1,
assert(coups(Coup_1)),
format('~w My guess ~w~n', [Coup, Guess]),
write('Bulls : '), read(Bulls),
write('Cows : '), read(Cows), nl,
assert('ia.pl':guess(Ms, [Bulls, Cows])),
Bulls = 4
; writeln('Sorry, I can''t find a solution !'), true).
add_1(X, Y) :-
Y is X + 1.
A game :
?- bulls_and_cows. 1 My guess 1234 Bulls : 0. Cows : 0. 2 My guess 5678 Bulls : 1. Cows : 2. 3 My guess 5769 Bulls : 0. Cows : 3. 4 My guess 8695 Bulls : 0. Cows : 3. 5 My guess 9876 Bulls : 4. Cows : 0. true .
[edit] PureBasic
#answerSize = 4
Structure history
answer.s
bulls.i
cows.i
EndStructure
Procedure evaluateGuesses(*answer.history, List remainingGuesses.s())
Protected i, cows, bulls
ForEach remainingGuesses()
bulls = 0: cows = 0
For i = 1 To #answerSize
If Mid(remainingGuesses(), i, 1) = Mid(*answer\answer, i, 1)
bulls + 1
ElseIf FindString(remainingGuesses(), Mid(*answer\answer, i, 1), 1)
cows + 1
EndIf
Next
If bulls <> *answer\bulls Or cows <> *answer\cows
DeleteElement(remainingGuesses())
EndIf
Next
EndProcedure
Procedure findPermutations(List permutations.s(), elementChar.s, permSize)
Protected i, j, stackDepth, elementCount = Len(elementChar) - 1, working.s = Space(permSize), *working = @working
permSize - 1
Dim stack(permSize) ;holds index states
Dim elements(elementCount)
Dim elementChar.c(elementCount)
For i = 0 To elementCount
elementChar(i) = PeekC(@elementChar + i * SizeOf(Character))
Next
i = 0
Repeat
While i <= elementCount
If elements(i) = 0
stack(stackDepth) = i
If stackDepth = permSize
For j = 0 To permSize
PokeC(*working + j * SizeOf(Character), elementChar(stack(j)))
Next
AddElement(permutations())
permutations() = working
Else
elements(i) = 1
stackDepth + 1
i = 0
Continue ;skip update
EndIf
EndIf
i + 1
Wend
stackDepth - 1
If stackDepth < 0
Break
EndIf
i = stack(stackDepth) + 1
elements(i - 1) = 0
ForEver
EndProcedure
If OpenConsole()
Define guess.s, guessNum, score.s, delimeter.s
NewList remainingGuesses.s()
NewList answer.history()
findPermutations(remainingGuesses(), "123456789", 4)
PrintN("Playing Bulls & Cows with " + Str(#answerSize) + " unique digits." + #CRLF$)
Repeat
If ListSize(remainingGuesses()) = 0
If answer()\bulls = #answerSize And answer()\cows = 0
PrintN(#CRLF$ + "Solved!")
Break ;exit Repeat/Forever
EndIf
PrintN(#CRLF$ + "BadScoring! Nothing fits the scores you gave.")
ForEach answer()
PrintN(answer()\answer + " -> [" + Str(answer()\bulls) + ", " + Str(answer()\cows) + "]")
Next
Break ;exit Repeat/Forever
Else
guessNum + 1
SelectElement(remainingGuesses(), Random(ListSize(remainingGuesses()) - 1))
guess = remainingGuesses()
DeleteElement(remainingGuesses())
Print("Guess #" + Str(guessNum) + " is " + guess + ". What does it score (bulls, cows)?")
score = Input()
If CountString(score, ",") > 0: delimeter = ",": Else: delimeter = " ": EndIf
AddElement(answer())
answer()\answer = guess
answer()\bulls = Val(StringField(score, 1, delimeter))
answer()\cows = Val(StringField(score, 2, delimeter))
evaluateGuesses(@answer(), remainingGuesses())
EndIf
ForEver
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()
CloseConsole()
EndIf
Sample output:
Playing Bulls & Cows with 4 unique digits. Guess #1 is 6273. What does it score (bulls, cows)?0,2 Guess #2 is 7694. What does it score (bulls, cows)?0,2 Guess #3 is 9826. What does it score (bulls, cows)?0,3 Guess #4 is 2569. What does it score (bulls, cows)?2,0 Guess #5 is 2468. What does it score (bulls, cows)?4,0 Solved! Press ENTER to exit
[edit] Python
from itertools import permutations
from random import shuffle
try:
raw_input
except:
raw_input = input
try:
from itertools import izip
except:
izip = zip
digits = '123456789'
size = 4
def parse_score(score):
score = score.strip().split(',')
return tuple(int(s.strip()) for s in score)
def scorecalc(guess, chosen):
bulls = cows = 0
for g,c in izip(guess, chosen):
if g == c:
bulls += 1
elif g in chosen:
cows += 1
return bulls, cows
choices = list(permutations(digits, size))
shuffle(choices)
answers = []
scores = []
print ("Playing Bulls & Cows with %i unique digits\n" % size)
while True:
ans = choices[0]
answers.append(ans)
#print ("(Narrowed to %i possibilities)" % len(choices))
score = raw_input("Guess %2i is %*s. Answer (Bulls, cows)? "
% (len(answers), size, ''.join(ans)))
score = parse_score(score)
scores.append(score)
#print("Bulls: %i, Cows: %i" % score)
found = score == (size, 0)
if found:
print ("Ye-haw!")
break
choices = [c for c in choices if scorecalc(c, ans) == score]
if not choices:
print ("Bad scoring? nothing fits those scores you gave:")
print (' ' +
'\n '.join("%s -> %s" % (''.join(an),sc)
for an,sc in izip(answers, scores)))
break
Sample output
Playing Bulls & Cows with 4 unique digits Guess 1 is 1935. Answer (Bulls, cows)? 0,2 Guess 2 is 4169. Answer (Bulls, cows)? 0,3 Guess 3 is 6413. Answer (Bulls, cows)? 1,1 Guess 4 is 9612. Answer (Bulls, cows)? 1,1 Guess 5 is 9481. Answer (Bulls, cows)? 3,0 Guess 6 is 9471. Answer (Bulls, cows)? 4,0 Ye-haw!
Sample bad output
If the scores are inconsistent you get output like:
Playing Bulls & Cows with 4 unique digits Guess 1 is 1549. Answer (Bulls, cows)? 0,0 Guess 2 is 3627. Answer (Bulls, cows)? 1,0 Bad scoring? nothing fits those scores you gave: 1549 -> (0, 0) 3627 -> (1, 0)
[edit] Ruby
size = 4
scores = []
guesses = []
puts "Playing Bulls & Cows with #{size} unique digits."
possible_guesses = ('1'..'9').to_a.permutation(size).to_a.shuffle
while
guesses << current_guess = possible_guesses.pop
print "Guess #{guesses.size} is #{current_guess.join}. Answer (bulls,cows)? "
scores << score = gets.split(',').map(&:to_i)
# handle win
break (puts "Yeah!") if score == [size,0]
# filter possible guesses
possible_guesses.select! do |pos_guess|
bulls = pos_guess.zip(current_guess).count{|digit_pair| digit_pair[0] == digit_pair[1]}
cows = pos_guess.count{|digit| current_guess.include?( digit )} - bulls
[bulls, cows] == score
end
# handle 'no possible guesses left'
if possible_guesses.empty? then
puts "Error in scoring?"
guesses.zip(scores).each{|g, (b, c)| puts "#{g.join} => bulls #{b} cows #{c}"}
break
end
end
Regular output
Playing Bulls & Cows with 4 unique digits. Guess 1 is 7158. Answer (bulls,cows)? 0,1 Guess 2 is 6843. Answer (bulls,cows)? 0,2 Guess 3 is 1439. Answer (bulls,cows)? 2,1 Guess 4 is 3479. Answer (bulls,cows)? 0,2 Guess 5 is 1234. Answer (bulls,cows)? 4,0 Yeah!
Wrong scoring
Playing Bulls & Cows with 4 unique digits. Guess 1 is 2857. Answer (bulls,cows)? 0,0 Guess 2 is 6419. Answer (bulls,cows)? 1,0 Error in scoring? 2857 => bulls 0 cows 0 6419 => bulls 1 cows 0
[edit] Tcl
package require struct::list
package require struct::set
proc scorecalc {guess chosen} {
set bulls 0
set cows 0
foreach g $guess c $chosen {
if {$g eq $c} {
incr bulls
} elseif {$g in $chosen} {
incr cows
}
}
return [list $bulls $cows]
}
# Allow override on command line
set size [expr {$argc ? int($argv) : 4}]
set choices {}
struct::list foreachperm p [split 123456789 ""] {
struct::set include choices [lrange $p 1 $size]
}
set answers {}
set scores {}
puts "Playing Bulls & Cows with $size unique digits\n"
fconfigure stdout -buffering none
while 1 {
set ans [lindex $choices [expr {int(rand()*[llength $choices])}]]
lappend answers $ans
puts -nonewline \
"Guess [llength $answers] is [join $ans {}]. Answer (Bulls, cows)? "
set score [scan [gets stdin] %d,%d]
lappend scores $score
if {$score eq {$size 0}} {
puts "Ye-haw!"
break
}
foreach c $choices[set choices {}] {
if {[scorecalc $c $ans] eq $score} {
lappend choices $c
}
}
if {![llength $choices]} {
puts "Bad scoring? nothing fits those scores you gave:"
foreach a $answers s $scores {
puts " [join $a {}] -> ([lindex $s 0], [lindex $s 1])"
}
break
}
}
Sample Output
Playing Bulls & Cows with 4 unique digits Guess 1 is 8527. Answer (Bulls, cows)? 0,1 Guess 2 is 5143. Answer (Bulls, cows)? 0,2 Guess 3 is 9456. Answer (Bulls, cows)? 2,0 Guess 4 is 9412. Answer (Bulls, cows)? 2,1 Guess 5 is 9481. Answer (Bulls, cows)? 3,0 Guess 6 is 9471. Answer (Bulls, cows)? 4,0 Ye-haw!
Sample Bad Output
Playing Bulls & Cows with 4 unique digits Guess 1 is 6578. Answer (Bulls, cows)? 0,0 Guess 2 is 3241. Answer (Bulls, cows)? 1,0 Bad scoring? nothing fits those scores you gave: 6578 -> (0, 0) 3241 -> (1, 0)
