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=={{header|Batch File}}==
=={{header|Batch File}}==
<lang dos>::
<lang dos>::
::Penney's Game Task from Wiki
::Penney's Game Task from Rosetta Code Wiki
::Batch File Implementation
::Batch File Implementation
::
::
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=={{header|R}}==
=={{header|R}}==
<lang rsplus>#===============================================================
<lang rsplus>#===============================================================
# Penney's Game Task from Wiki
# Penney's Game Task from Rosetta Code Wiki
# R implementation
# R implementation
#===============================================================
#===============================================================

Revision as of 22:41, 18 January 2017

Task
Penney's game
You are encouraged to solve this task according to the task description, using any language you may know.

Penney's game   is a game where two players bet on being the first to see a particular sequence of   heads or tails   in consecutive tosses of a   fair coin.

It is common to agree on a sequence length of three then one player will openly choose a sequence, for example: 

 Heads,  Tails,  Heads,    or 
 HTH                       for short.

The other player on seeing the first players choice will choose his sequence.

The coin is tossed and the first player to see his sequence in the sequence of coin tosses wins.


Example

One player might choose the sequence   HHT   and the other   THT.  

Successive coin tosses of   HTTHT   gives the win to the second player as the last three coin tosses are his sequence.


Task

Create a program that tosses the coin, keeps score and plays Penney's game against a human opponent.

  •   Who chooses and shows their sequence of three should be chosen randomly.
  •   If going first, the computer should randomly choose its sequence of three.
  •   If going second, the computer should automatically play the optimum sequence.
  •   Successive coin tosses should be shown.


Show output of a game where the computer chooses first and a game where the user goes first here on this page.


See also



Batch File

<lang dos>::

Penney's Game Task from Rosetta Code Wiki
Batch File Implementation
Please Directly Open the Batch File to play...

@echo off setlocal enabledelayedexpansion title The Penney's Game Batch File

set cpu=0&set you=0 cls echo. echo Penney's Game echo Batch File Implementation

main

set you_bet=&set cpu_bet= echo.&echo --------------------------------------------------------&echo. echo CPU's Score: %cpu% Your Score: %you% echo. <nul set /p "dummy=Heads I start, Tails you start..." set /a startrnd=%random%%%2 set firsttoss=Tails&set func=optimal if %startrnd%==1 (set firsttoss=Heads&set func=rndbet) ping -n 3 localhost >nul <nul set /p "dummy=. %firsttoss%^!" echo.&echo. goto %func%

rndbet

set /a "seq1=%random%%%2","seq2=%random%%%2","seq3=%random%%%2" set binary=%seq1%%seq2%%seq3% set cpu_bet=%binary:1=H% set cpu_bet=%cpu_bet:0=T% echo I will bet first. So, my bet sequence will be %cpu_bet%.

again1

set /p "you_bet=What will be your bet sequence? " call :validate again1 echo.&echo So, you're feeling lucky on %you_bet%. We'll see... goto succesivetossing

optimal

echo Ok. You will bet first.

again2

set /p "you_bet=What will be your bet sequence? " call :validate again2 set seq1=%you_bet:~0,1%&set seq2=%you_bet:~1,1% set new_seq1=T if /i %seq2%==T set new_seq1=H set cpu_bet=%new_seq1%%seq1%%seq2% echo.&echo Hmm... My bet will be %cpu_bet%. We'll see who's lucky...

succesivetossing

set toses=&set cnt=0 echo. <nul set /p "dummy=Tosses: "

tossloop

call :tossgen <nul set /p dummy=%toss% ping -n 2 localhost >nul set /a newline=%cnt%%%60 if %newline%==59 ( echo. <nul set /p "dummy=. " ) if "%toses:~-3,3%"=="%cpu_bet%" goto iwin if "%toses:~-3,3%"=="%you_bet%" goto uwin set /a cnt+=1&goto tossloop

tossgen

set /a rand=%random%%%2 set toss=T if %rand%==0 set toss=H set toses=%toses%%toss% goto :EOF

iwin

set /a cpu+=1&set newgame= echo.&echo. echo I Win^^! Better Luck Next Time... echo. set /p "newgame=[Type Y if U Wanna Beat Me, or Else, Exit...] " if /i "!newgame!"=="Y" goto :main exit

uwin

set /a you+=1&set newgame= echo.&echo. echo Argh, You Win^^! ...But One Time I'll Beat You. echo. set /p "newgame=[Type Y for Another Game, or Else, Exit...] " if /i "!newgame!"=="Y" goto :main exit

validate

echo "!you_bet!"|findstr /r /c:"^\"[hHtT][hHtT][hHtT]\"$">nul || ( echo [Invalid Input...]&echo.&goto %1 ) if /i "!you_bet!"=="%cpu_bet%" (echo [Bet something different...]&echo.&goto %1) for %%i in ("t=T" "h=H") do set "you_bet=!you_bet:%%~i!" goto :EOF</lang>

Output:

Note: The outputs of tosses are 'delayed' just to make the game a little more dramatic. 

Penney's Game
Batch File Implementation

--------------------------------------------------------

CPU's Score: 0 Your Score: 0

Heads I start, Tails you start....   Heads!

I will bet first. So, my bet sequence will be THH.
What will be your bet sequence? tTh

So, you're feeling lucky on TTH. We'll see...

Tosses:    HHTHTHH

I Win! Better Luck Next Time...

[Type Y if U Wanna Beat Me, or Else, Exit...] y

--------------------------------------------------------

CPU's Score: 1 Your Score: 0

Heads I start, Tails you start....   Tails!

Ok. You will bet first.
What will be your bet sequence? tHt

Hmm... My bet will be TTH. We'll see who's lucky...

Tosses:    HTTH

I Win! Better Luck Next Time...

[Type Y if U Wanna Beat Me, or Else, Exit...]

BBC BASIC

<lang bbcbasic>REM >penney PRINT "*** Penney's Game ***" REPEAT 

 PRINT ' "Heads you pick first, tails I pick first."
 PRINT "And it is... ";
 WAIT 100
 ht% = RND(0 - TIME) AND 1
 IF ht% THEN
   PRINT "heads!"
   PROC_player_chooses(player$)
   computer$ = FN_optimal(player$)
   PRINT "I choose "; computer$; "."
 ELSE
   PRINT "tails!"
   computer$ = FN_random
   PRINT "I choose "; computer$; "."
   PROC_player_chooses(player$)
 ENDIF
 PRINT "Starting the game..." ' SPC 5;
 sequence$ = ""
 winner% = FALSE
 REPEAT
   WAIT 100
   roll% = RND AND 1
   IF roll% THEN
     sequence$ += "H"
     PRINT "H  ";
   ELSE
     PRINT "T  ";
     sequence$ += "T"
   ENDIF
   IF RIGHT$(sequence$, 3) = computer$ THEN
     PRINT ' "I won!"
     winner% = TRUE
   ELSE
     IF RIGHT$(sequence$, 3) = player$ THEN
       PRINT ' "Congratulations! You won."
       winner% = TRUE
     ENDIF
   ENDIF
 UNTIL winner%
 REPEAT
   valid% = FALSE
   INPUT "Another game? (Y/N) " another$
   IF INSTR("YN", another$) THEN valid% = TRUE
 UNTIL valid%

UNTIL another$ = "N" PRINT "Thank you for playing!" END

DEF PROC_player_chooses(RETURN sequence$) LOCAL choice$, valid%, i% REPEAT 

 valid% = TRUE
 PRINT "Enter a sequence of three choices, each of them either H or T:"
 INPUT "> " sequence$
 IF LEN sequence$ <> 3 THEN valid% = FALSE
 IF valid% THEN
   FOR i% = 1 TO 3
     choice$ = MID$(sequence$, i%, 1)
     IF choice$ <> "H" AND choice$ <> "T" THEN valid% = FALSE
   NEXT
 ENDIF

UNTIL valid% ENDPROC

DEF FN_random LOCAL sequence$, choice%, i% sequence$ = "" FOR i% = 1 TO 3 

 choice% = RND AND 1
 IF choice% THEN sequence$ += "H" ELSE sequence$ += "T"

NEXT = sequence$

DEF FN_optimal(sequence$) IF MID$(sequence$, 2, 1) = "H" THEN 

 = "T" + LEFT$(sequence$, 2)

ELSE 

 = "H" + LEFT$(sequence$, 2)

ENDIF</lang>

Output:
*** Penney's Game ***

Heads you pick first, tails I pick first.
And it is... heads!
Enter a sequence of three choices, each of them either H or T:
> HTT
I choose HHT.
Starting the game...
     H  H  H  H  H  T  
I won!
Another game? (Y/N) Y

Heads you pick first, tails I pick first.
And it is... tails!
I choose HTH.
Enter a sequence of three choices, each of them either H or T:
> HHT
Starting the game...
     T  T  H  H  H  H  T  
Congratulations! You won.
Another game? (Y/N) N
Thank you for playing!

C

This solution stores the sequences in bit-packed integers. With minor adjustments, this can be extended to allow larger sequence lengths beyond the required 3. However, the ai's algorithm for the perfect choice would need to be altered. More robust methods of input could be chosen, as scanf is generally fairly unsafe. A safer alternative would be to use something like fgets, and parse the input string ourselves. <lang C>

  1. include <stdio.h>
  2. include <stdlib.h>
  3. include <time.h>
  1. define SEQLEN 3

int getseq(char *s) { 

   int r = 0;
   int i = 1 << (SEQLEN - 1);

   while (*s && i) {
       switch (*s++) {
           case 'H':
           case 'h':
               r |= i;
               break;
           case 'T':
           case 't':
               /* 0 indicates tails, this is 0, so do nothing */
               break;
           default:
               return -1;
       }
       i >>= 1;
   }

   return r;

}

void printseq(int seq) { 

   int i;
   for (i = SEQLEN - 1; i >= 0; --i)
       printf("%c", seq & (1 << i) ? 'h' : 't');

}

int getuser(void) { 

   int user;
   char s[SEQLEN + 1];

   printf("Enter your sequence of %d (h/t): ", SEQLEN);
   while (1) {
       /* This needs to be manually changed if SEQLEN is changed */
       if (scanf("%3s", s) != 1) exit(1);
       if ((user = getseq(s)) != -1) return user;
       printf("Please enter only h/t characters: ");
   }

}

int getai(int user) { 

   int ai;

   printf("Computers sequence of %d is: ", SEQLEN);
   /* The ai's perfect choice will only be perfect for SEQLEN == 3 */
   if (user == -1)
       ai = rand() & (1 << SEQLEN) - 1;
   else
       ai = (user >> 1) | ((~user << 1) & (1 << SEQLEN - 1));

   printseq(ai);
   printf("\n");
   return ai;

}

int rungame(int user, int ai) { 

   /* Generate first SEQLEN flips. We only need to store the last SEQLEN
    * tosses at any one time. */
   int last3 = rand() & (1 << SEQLEN) - 1;

   printf("Tossed sequence: ");
   printseq(last3);
   while (1) {
       if (user == last3) {
           printf("\nUser wins!\n");
           return 1;
       }

       if (ai == last3) {
           printf("\nAi wins!\n");
           return 0;
       }

       last3 = ((last3 << 1) & (1 << SEQLEN) - 2) | (rand() & 1);
       printf("%c", last3 & 1 ? 'h' : 't');
   }

}

int main(void) { 

   srand(time(NULL));
   int playerwins = 0;
   int totalgames = 0;

   /* Just use ctrl-c for exit */
   while (1) {
       int user = -1;
       int ai   = -1;

       printf("\n");
       if (rand() & 1) {
           ai   = getai(user);
           user = getuser();
       }
       else {
           user = getuser();
           ai   = getai(user);
       }
       
       playerwins += rungame(user, ai);
       totalgames++;

       printf("You have won %d out of %d games\n", playerwins, totalgames);
       printf("=================================\n");
   }

   return 0;

} </lang>

Output:

Enter your sequence of 3 (h/t): tth
Computers sequence of 3 is: htt
Tossed sequence: ttth
User wins!
You have won 1 out of 1 games
=================================

Enter your sequence of 3 (h/t): tth
Computers sequence of 3 is: htt
Tossed sequence: thhhthhhthhhtt
Ai wins!
You have won 1 out of 2 games
=================================

C++

<lang cpp>

  1. include <time.h>
  2. include <iostream>
  3. include <string>

using namespace std;

class penney { public: 

   penney()
   { pW = cW = 0;  }
   void gameLoop()
   {

string a; while( true ) { playerChoice = computerChoice = ""; if( rand() % 2 ) { computer(); player(); } else { player(); computer(); }

play();

cout << "[Y] to play again "; cin >> a; if( a[0] != 'Y' && a[0] != 'y' ) { cout << "Computer won " << cW << " times." << endl << "Player won " << pW << " times."; break; } cout << endl << endl; 

       }
   }

private: 

   void computer()
   {
       if( playerChoice.length() == 0 )

{ for( int x = 0; x < 3; x++ ) computerChoice.append( ( rand() % 2 ) ? "H" : "T", 1 ); } else { computerChoice.append( playerChoice[1] == 'T' ? "H" : "T", 1 ); computerChoice += playerChoice.substr( 0, 2 ); } cout << "Computer's sequence of three is: " << computerChoice << endl; 

   }
   void player()
   {

cout << "Enter your sequence of three (H/T) "; cin >> playerChoice; 

   }
   void play()
   {

sequence = ""; while( true ) { sequence.append( ( rand() % 2 ) ? "H" : "T", 1 ); if( sequence.find( playerChoice ) != sequence.npos ) { showWinner( 1 ); break; } else if( sequence.find( computerChoice ) != sequence.npos ) { showWinner( 0 ); break; } } 

   }
   void showWinner( int i )
   {

string s; if( i ) { s = "Player wins!"; pW++; } else { s = "Computer wins!"; cW++; } cout << "Tossed sequence: " << sequence << endl << s << endl << endl; 

   }
   string playerChoice, computerChoice, sequence;
   int pW, cW;

}; int main( int argc, char* argv[] ) { 

   srand( static_cast<unsigned>( time( NULL ) ) );
   penney game; game.gameLoop();
   return 0;

} </lang>

Output:
Computer's sequence of three is: HHH
Enter your sequence of three (H/T) THH
Tossed sequence: TTHTTTTTTTTTTTHTHTTTHTTHTTHH
Player wins!

[Y] to play again y

Enter your sequence of three (H/T) HTH
Computer's sequence of three is: HHT
Tossed sequence: THHT
Computer wins!

[Y] to play again

D

Translation of: Python

<lang d>void main() { 

   import std.stdio, std.random, std.algorithm, std.string,
          std.conv, std.range, core.thread;

   immutable first = uniform(0, 2) == 0;

   string you, me;
   if (first) {
       me = 3.iota.map!(_ => "HT"[uniform(0, $)]).text;
       writefln("I choose first and will win on first seeing %s in the list of tosses", me);
       while (you.length != 3 || you.any!(c => !c.among('H', 'T')) || you == me) {
           "What sequence of three Heads/Tails will you win with: ".write;
           you = readln.strip;
       }
   } else {
       while (you.length != 3 || you.any!(c => !c.among('H', 'T'))) {
           "After you: What sequence of three Heads/Tails will you win with: ".write;
           you = readln.strip;
       }
       me = (you[1] == 'T' ? 'H' : 'T') ~ you[0 .. 2];
       writefln("I win on first seeing %s in the list of tosses", me);
   }

   "Rolling:\n  ".write;
   string rolled;
   while (true) {
       rolled ~= "HT"[uniform(0, $)];
       rolled.back.write;
       if (rolled.endsWith(you))
           return "\n  You win!".writeln;
       if (rolled.endsWith(me))
           return "\n  I win!".writeln;
       Thread.sleep(1.seconds);
   }

}</lang> The output is the same as the Python entry.

Elixir

Translation of: Ruby

<lang elixir>defmodule Penney do 

 @toss [:Heads, :Tails]
 
 def game(score \\ {0,0})
 def game({iwin, ywin}=score) do
   IO.puts "Penney game score  I : #{iwin}, You : #{ywin}"
   [i, you] = @toss
   coin = Enum.random(@toss)
   IO.puts "#{i} I start, #{you} you start ..... #{coin}"
   {myC, yC} = setup(coin)
   seq = for _ <- 1..3, do: Enum.random(@toss)
   IO.write Enum.join(seq, " ")
   {winner, score} = loop(seq, myC, yC, score)
   IO.puts "\n #{winner} win!\n"
   game(score)
 end
 
 defp setup(:Heads) do
   myC = Enum.shuffle(@toss) ++ [Enum.random(@toss)]
   joined = Enum.join(myC, " ")
   IO.puts "I chose  : #{joined}"
   {myC, yourChoice}
 end
 defp setup(:Tails) do
   yC = yourChoice
   myC = (@toss -- [Enum.at(yC,1)]) ++ Enum.take(yC,2)
   joined = Enum.join(myC, " ")
   IO.puts "I chose  : #{joined}"
   {myC, yC}
 end
 
 defp yourChoice do
   IO.write "Enter your choice (H/T) "
   choice = read([])
   IO.puts "You chose: #{Enum.join(choice, " ")}"
   choice
 end
 
 defp read([_,_,_]=choice), do: choice
 defp read(choice) do
   case IO.getn("") |> String.upcase do
     "H" -> read(choice ++ [:Heads])
     "T" -> read(choice ++ [:Tails])
     _   -> read(choice)
   end
 end
 
 defp loop(myC, myC, _, {iwin, ywin}), do: {"I", {iwin+1, ywin}}
 defp loop(yC,  _,  yC, {iwin, ywin}), do: {"You", {iwin, ywin+1}}
 defp loop(seq, myC, yC, score) do
   append = Enum.random(@toss)
   IO.write " #{append}"
   loop(tl(seq)++[append], myC, yC, score)
 end

end

Penney.game</lang>

Output:
Penney game score  I : 0, You : 0
Heads I start, Tails you start ..... Heads
I chose  : Tails Heads Heads
Enter your choice (H/T) TTH
You chose: Tails Tails Heads
Heads Heads Tails Tails Tails Tails Heads
 You win!

Penney game score  I : 0, You : 1
Heads I start, Tails you start ..... Tails
Enter your choice (H/T) THT
You chose: Tails Heads Tails
I chose  : Tails Tails Heads
Tails Heads Heads Heads Tails Tails Heads
 I win!

Penney game score  I : 1, You : 1
Heads I start, Tails you start ..... Tails
Enter your choice (H/T)

Go

<lang Go> package main import "fmt" import "math/rand" func main(){ var a1,a2,a3,y,match,j,k int var inp string y=1 for y==1{ fmt.Println("Enter your sequence:") fmt.Scanln(&inp) var Ai [3] int var user [3] int for j=0;j<3;j++{ if(inp[j]==104){ user[j]=1 }else{ user[j]=0 } } for k=0;k<3;k++{ Ai[k]=rand.Intn(2) } for user[0]==Ai[0]&&user[1]==Ai[1]&&user[2]==Ai[2]{ for k=0;k<3;k++{ Ai[k]=rand.Intn(2) } } fmt.Println("You gave the sequence:") printht(user) fmt.Println() fmt.Println("The computer generated sequence is:") printht(Ai) fmt.Println() a1=rand.Intn(2) a2=rand.Intn(2) a3=rand.Intn(2) fmt.Print("The generated sequence is:") printh(a1) printh(a2) printh(a3) match=0 for match==0{ if(matches(user,a1,a2,a3)==1){ fmt.Println() fmt.Println("You have won!!!") match=1 }else if(matches(Ai,a1,a2,a3)==1){ fmt.Println() fmt.Println("You lost!! Computer wins") match=1 }else{ a1=a2 a2=a3 a3=rand.Intn(2) printh(a3) } } fmt.Println("Do you want to continue(0/1):") fmt.Scanln(&y) } } func printht(a [3] int) int{ var i int for i=0;i<3;i++{ if(a[i]==1){ fmt.Print("h") }else{ fmt.Print("t") } } return 1 } func printh(a int) int{ if(a==1){ fmt.Print("h") }else{ fmt.Print("t") } return 1 } func matches(a [3] int,p int,q int,r int) int{ if(a[0]==p&&a[1]==q&&a[2]==r){ return 1 }else{ return 0 } } </lang> Output: 

Enter your sequence:
tht
You gave the sequence:
tht
The computer generated sequence is:
hhh
The generated sequence is:hhtht
You have won!!!
Do you want to continue(0/1):

Haskell

<lang Haskell>import qualified Data.List as L import System.IO import System.Random

data CoinToss = H | T deriving (Read, Show, Eq)

parseToss :: String -> [CoinToss] parseToss [] = [] parseToss (s:sx) 

 | s == 'h' || s == 'H' = H : parseToss sx
 | s == 't' || s == 'T' = T : parseToss sx
 | otherwise = parseToss sx

notToss :: CoinToss -> CoinToss notToss H = T notToss T = H

instance Random CoinToss where 

 random g = let (b, gb) = random g in (if b then H else T, gb)
 randomR = undefined

prompt :: (Read a) => String -> String -> (String -> Maybe a) -> IO a prompt msg err parse = do 

 putStrLn msg
 line <- getLine
 let ans = parse line
 case ans of
   Nothing   -> do
     putStrLn err
     prompt msg err parse
   Just ansB -> return ansB

showCat :: (Show a) => [a] -> String showCat = concatMap show

data Winner = Player | CPU

-- This may never terminate. runToss :: (RandomGen g) => [CoinToss] -> [CoinToss] -> g -> ([CoinToss], Winner) runToss player cpu gen = 

 let stream = randoms gen
     run ss@(s:sx)
       | L.isPrefixOf player ss = player
       | L.isPrefixOf cpu ss    = cpu
       | otherwise              = s : run sx
     winner = run stream
 in if L.isSuffixOf player winner
    then (winner, Player)
    else (winner, CPU)

game :: (RandomGen g, Num a, Show a) => Bool -> a -> a -> g -> IO () game cpuTurn playerScore cpuScore gen = do 

 putStrLn $ "\nThe current score is CPU: " ++ show cpuScore
   ++ ", You: " ++ show playerScore

 let (genA, genB) = split gen
     promptPlayer check =
       prompt "Pick 3 coin sides: " "Invalid input." $ \s ->
         let tosses = parseToss s in
         if check tosses then Just tosses else Nothing
     promptCpu x  = putStrLn $ "I have chosen: " ++ showCat x

 (tosses, winner) <-
   if cpuTurn
   then do
     let cpuChoice = take 3 $ randoms gen
     promptCpu cpuChoice
     playerChoice <- promptPlayer $ \n -> n /= cpuChoice && 3 == length n
     return $ runToss playerChoice cpuChoice genA
   else do
     playerChoice <- promptPlayer $ \n -> 3 == length n
     let cpuChoice = case playerChoice of [a,b,_] -> [notToss b, a, b]
     promptCpu cpuChoice
     return $ runToss playerChoice cpuChoice genA

 putStrLn $ "The sequence tossed was: " ++ showCat tosses

 case winner of
   Player -> do
     putStrLn "You win!"
     game (not cpuTurn) (playerScore + 1) cpuScore genB
   CPU -> do
     putStrLn "I win!"
     game (not cpuTurn) playerScore (cpuScore + 1) genB

main :: IO () main = do 

 hSetBuffering stdin LineBuffering
 stdgen <- getStdGen
 let (cpuFirst, genA) = random stdgen
 game cpuFirst 0 0 genA</lang>
Output:
The current score is CPU: 0, You: 0
Pick 3 coin sides:
HTH
I have chosen: HHT
The sequence tossed was: TTTTTTHHT
I win!

The current score is CPU: 1, You: 0
I have chosen: TTT
Pick 3 coin sides:
HTT
The sequence tossed was: HTT
You win!

The current score is CPU: 1, You: 1
Pick 3 coin sides:

J

Solution: <lang J>require 'format/printf numeric'

randomize NB. randomize seed for new session

Vals=: 'HT' NB. valid values input=: 1!:1@<&1: NB. get input from user prompt=: input@echo NB. prompt user for input checkInput=: 'Choose 3 H/Ts' assert (Vals e.~ ]) , 3 = # getUserSeq=: (] [ checkInput)@toupper@prompt choose1st=: Vals {~ 3 ?@$ 2: NB. computer chooses 1st choose2nd=: (0 1 1=1 0 1{])&.(Vals&i.) NB. computer chooses 2nd

playPenney=: verb define 

 if. ?2 do.                               NB. randomize first chooser
   Comp=. choose1st 
   'Computer chose %s' printf <Comp
   You=. getUserSeq 'Choose a sequence of three coin tosses (H/T):'
   'Choose a different sequence to computer' assert You -.@-: Comp
 else.
   You=. getUserSeq 'Choose a sequence of three coin tosses (H/T):'
   Comp=. choose2nd You
   'Computer chose %s ' printf <Comp
 end.
 Tosses=. Vals {~ 100 ?@$ 2
 Result=. (Comp,:You) {.@I.@E."1 Tosses
 'Toss sequence is %s' printf < (3 + <./ Result) {. Tosses
 echo ('No result';'You win!';'Computer won!') {::~ *-/ Result

)</lang> Usage: <lang J> playPenney Computer chose TTT Choose a sequence of three coin tosses (H/T): HTT Toss sequence is TTHHTT You win! 

  playPenney

Choose a sequence of three coin tosses (H/T): HTT Computer chose HHT Toss sequence is HTHTT You win!</lang>

Java

<lang java>import java.util.*;

public class PenneysGame { 

   public static void main(String[] args) {
       Random rand = new Random();

       String compChoice = "", playerChoice;
       if (rand.nextBoolean()) {

           for (int i = 0; i < 3; i++)
               compChoice += "HT".charAt(rand.nextInt(2));
           System.out.printf("Computer chooses %s%n", compChoice);

           playerChoice = prompt(compChoice);

       } else {

           playerChoice = prompt(compChoice);

           compChoice = "T";
           if (playerChoice.charAt(1) == 'T')
               compChoice = "H";
           compChoice += playerChoice.substring(0, 2);
           System.out.printf("Computer chooses %s%n", compChoice);
       }

       String tossed = "";
       while (true) {
           tossed += "HT".charAt(rand.nextInt(2));
           System.out.printf("Tossed %s%n" , tossed);
           if (tossed.endsWith(playerChoice)) {
               System.out.println("You win!");
               break;
           }
           if (tossed.endsWith(compChoice)) {
               System.out.println("Computer wins!");
               break;
           }
       }
   }

   private static String prompt(String otherChoice) {
       Scanner sc = new Scanner(System.in);
       String s;
       do {
           System.out.print("Choose a sequence: ");
           s = sc.nextLine().trim().toUpperCase();
       } while (!s.matches("[HT]{3}") || s.equals(otherChoice));
       return s;
   }

}</lang> 

Computer chooses HTH
Choose a sequence: hhh
Tossed H
Tossed HH
Tossed HHH
You win!

Choose a sequence: tth
Computer chooses HTT
Tossed H
Tossed HT
Tossed HTH
Tossed HTHH
Tossed HTHHT
Tossed HTHHTT
Computer wins!

Julia

Functions <lang Julia> const SLEN = 3

autobet() = randbool(SLEN) function autobet(ob::BitArray{1}) 

   rlen = length(ob)
   2 < rlen || return ~ob
   3 < rlen || return [~ob[2], ob[1:2]]
   opt = falses(rlen)
   opt[1] = true
   opt[end-1:end] = true
   ob != opt || return ~opt
   return opt

end autobet(ob::Array{Bool,1}) = autobet(convert(BitArray{1}, ob))

function pgencode{T<:String}(a::T) 

   b = uppercase(a)
   0 < length(b) || return trues(0)
   !ismatch(r"[^HT]+", b) || error(@sprintf "%s is not a HT sequence" a)
   b = split(b, "")
   b .== "H"

end pgdecode(a::BitArray{1}) = join([i ? "H" : "T" for i in a], "")

function humanbet() 

   b = ""
   while length(b) != SLEN  || ismatch(r"[^HT]+", b)
       print("Your bet? ")
       b = uppercase(chomp(readline()))
   end
   return b

end </lang>

Game Setup <lang Julia> println("Playing Penney's Game Against the computer.")

if randbool() 

   mach = autobet()
   println(@sprintf "The computer bet first, chosing %s." pgdecode(mach))
   println("Now you can bet.")
   human = pgencode(humanbet())

else 

   println("You bet first.")
   human = pgencode(humanbet())
   mach = autobet(human)

end print(@sprintf "You bet %s " pgdecode(human)) println(@sprintf "and the computer bet %s." pgdecode(mach)) </lang>

Game Play <lang Julia> pg = randbool(SLEN) pgtail = copy(pg) while pgtail != mach && pgtail != human 

   push!(pg, randbool())
   pgtail = [pgtail[2:end], pg[end]]

end

println(@sprintf("This game lasted %d turns yielding\n %s", 

                length(pg), pgdecode(pg)))

if human == mach 

   println("so you and the computer tied.")

elseif pgtail == mach 

   println("so the computer won.")

else 

   println("so you won.")

end </lang>

Output:
$ julia penneys_game.jl
Playing Penney's Game Against the computer.
You bet first.
Your bet? tht
You bet THT and the computer bet TTH.
This game lasted 10 turns yielding
    HHTTTTTTTH
so the computer won.

$ julia penneys_game.jl
Playing Penney's Game Against the computer.
You bet first.
Your bet? hhh
You bet HHH and the computer bet THH.
This game lasted 8 turns yielding
    TTHTHTHH
so the computer won.

$ julia penneys_game.jl
Playing Penney's Game Against the computer.
The computer bet first, chosing HTT.
Now you can bet.
Your bet? hht
You bet HHT and the computer bet HTT.
This game lasted 6 turns yielding
    TTHHHT
so you won.

$ julia penneys_game.jl
Playing Penney's Game Against the computer.
The computer bet first, chosing HTT.
Now you can bet.
Your bet? hht
You bet HHT and the computer bet HTT.
This game lasted 6 turns yielding
    THTHHT
so you won.

$ julia penneys_game.jl
Playing Penney's Game Against the computer.
You bet first.
Your bet? htt
You bet HTT and the computer bet HHT.
This game lasted 10 turns yielding
    TTTTHHHHHT
so the computer won.

Perl

<lang perl>

  1. !usr/bin/perl

use 5.020; use strict; use warnings;

  1. Choose who goes first

binaryRand() == 0 ? flipCoin(userFirst()) : flipCoin(compFirst());

  1. Return a randomly generated 1 or 0

sub binaryRand { 

   return int(rand(2));

}

  1. Converts 1's and 0's to H's and T's, respectively.

sub convert { 

   my $randNum = binaryRand();
   if($randNum == 0)
   {
       return "T"
   }
   else
   {
       return "H";
   }

}

  1. Prompts for and returns a user's sequence of 3

sub uSeq { 

   print("Please enter a sequence of 3 of \"H\" and \"T\". EG: HHT\n>");
   my $uString = <STDIN>;

   while(1)
   {
       #Make it uppercase and validate input
       chomp($uString);
       $uString = uc $uString;
       #Check length and content (H's and T's only!)
       if(length $uString == 3 && (substr($uString, 0, 1) =~ /[HT]/ &&
                                   substr($uString, 1, 1) =~ /[HT]/ &&
                                   substr($uString, 2, 1) =~ /[HT]/))
       {
           last;
       }
       else
       {
           print("Error, try again. \n");
           print("Please enter a sequence of 3 of \"H\" and \"T\". EG: HHT\n");
           $uString = <STDIN>;
       }
   }
   return $uString;

}

  1. Returns an array with two elements: [0] user's seq, [1] random computer seq.

sub compFirst { 

   my $cSeq;
   #Randomly draw a sequence of 3
   for(my $i = 0; $i < 3; $i++)
   {
       $cSeq = $cSeq . convert();
   }

   print("The computer guesses first:\ncomp- $cSeq\n");
   my $uSeq = uSeq();
   print("user- $uSeq\n");
   my @seqArr = ($uSeq, $cSeq);
   return @seqArr;

}

  1. Returns an array with two elements: [0] user's seq, [1] optimal computer seq.

sub userFirst { 

   print("The user quesses first:\n");
   my $uSeq = uSeq();
   my $cSeq;
   #Generate the optimal sequence based on $uSeq
   my $middle = substr($uSeq, 1, 1);
   $middle eq "H" ? $cSeq = "T" : $cSeq = "H";
   $cSeq = $cSeq . substr($uSeq, 0, 2); 

   print("user- $uSeq\ncomp- $cSeq\n");
   my @seqArr = ($uSeq, $cSeq);
   return @seqArr;

}

  1. Flips a coin, checking both sequences against the contents of the given array

sub flipCoin { 

   my ($uSeq, $cSeq) = @_;
   my $coin;
   while(1)
   {
       $coin = $coin . convert();
       if($coin =~ m/$uSeq/)
       {
           print("The sequence of tosses was: $coin\n");
           say("The player wins! ");
           last;
       }
       elsif($coin =~ m/$cSeq/)
       {
           print("The sequence of tosses was: $coin\n");
           say("The computer wins! ");
           last;
       }
   }

} </lang>

Output:
The computer guesses first:
comp- HHH
Please enter a sequence of 3 of "H" and "T". EG: HHT
>thh
user- THH
The sequence of tosses was: HTTHTTHTHTHTTTHTTTHH
The player wins! 
================================================
The user quesses first:
Please enter a sequence of 3 of "H" and "T". EG: HHT
>hht
user- HHT
comp- HHH
The sequence of tosses was: THHH
The computer wins!

Perl 6

<lang perl6>enum Coin <Heads Tails>; enum Yay <Yay Good Super Hah Ooh Yipee Sweet Cool Yes Haha>; enum Boo <Drat Darn Crumb Oops Rats Bah Criminy Argh Shards>; enum Bozo «'Dude' 'Cha' 'Bzzt' 'Hey' 'Silly dilly' 'Say what!?' 'You numbskull'»;

sub flipping { 

   for 1..4 {
       print "-\b";  sleep .1;
       print "\\\b"; sleep .1;
       print "|\b";  sleep .1;
       print "/\b";  sleep .1;
   }

}

sub your-choice($p is copy) { 

   loop (my @seq; @seq != 3; $p = "{Bozo.pick}! Please pick exactly 3: ") {
       @seq = prompt($p).uc.comb(/ H | T /).map: {
           when 'H' { Heads }
           when 'T' { Tails }
       }
   }
   @seq;

}

repeat until prompt("Wanna play again? ").lc ~~ /^n/ { 

   my $mefirst = Coin.roll;
   print tc "$mefirst I start, {Coin(+!$mefirst).lc} you start, flipping...\n\t";
   flipping;
   say my $flip = Coin.roll;

   my @yours;
   my @mine;

   if $flip == $mefirst {
       print "{Yay.pick}! I get to choose first, and I choose: "; sleep 2; say @mine = Coin.roll(3);
       @yours = your-choice("Now you gotta choose: ");
       while @yours eqv @mine {
           say "{Bozo.pick}! We'd both win at the same time if you pick that!";
           @yours = your-choice("Pick something different from me: ");
       }
       say "So, you'll win if we see: ", @yours;
   }
   else {
       @yours = your-choice("{Boo.pick}! First you choose: ");
       say "OK, you'll win if we see: ", @yours;
       print "In that case, I'll just randomly choose: "; sleep 2; say @mine = Coin(+!@yours[1]), @yours[0,1];
   }
    
   sub check($a,$b,$c) {
       given [$a,$b,$c] {
           when @mine  { say "\n{Yay.pick}, I win, and you lose!"; Nil }
           when @yours { say "\n{Boo.pick}, you win, but I'll beat you next time!"; Nil }
           default     { Coin.roll }
       }
   }

   sleep 1;
   say < OK! Ready? Right... So... Yo!>.pick;
   sleep .5;
   say ("Pay attention now!",
       "Watch closely!",
       "Let's do it...",
       "You feeling lucky?",
       "No way you gonna win this...",
       "Can I borrow that coin again?").pick;
   sleep 1;
   print "Here we go!\n\t";
   for Coin.roll(3), &check ...^ :!defined {
       flipping;
       print "$_ ";
   }

}</lang>

Output:

Note: the actual run displays a little coin-flipping animation, but that won't show up here: 

Heads I start, tails you start, flipping...
	Heads
Yipee! I get to choose first, and I choose: Heads Heads Tails
Now you gotta choose: tth
So, you'll win if we see: Tails Tails Heads
Yo!
Can I borrow that coin again?
Here we go!
	Tails Tails Tails Tails Tails Heads 
Argh, you win, but I'll beat you next time!
Wanna play again? y
Tails I start, heads you start, flipping...
	Tails
Yes! I get to choose first, and I choose: Heads Tails Tails
Now you gotta choose: H T T
Dude! We'd both win at the same time if you pick that!
Pick something different from me: heads tails tails
Silly dilly! We'd both win at the same time if you pick that!
Pick something different from me: h,h,h
So, you'll win if we see: Heads Heads Heads
OK!
You feeling lucky?
Here we go!
	Tails Tails Tails Heads Heads Heads 
Drat, you win, but I'll beat you next time!
Wanna play again? y
Heads I start, tails you start, flipping...
	Tails
Shards! First you choose: tht
OK, you'll win if we see: Tails Heads Tails
In that case, I'll just randomly choose: Tails Tails Heads
Right...
Pay attention now!
Here we go!
	Heads Tails Tails Heads 
Hah, I win, and you lose!
Wanna play again? n

Python

<lang python>from __future__ import print_function import random from time import sleep

first = random.choice([True, False])

you = if first: 

   me = .join(random.sample('HT'*3, 3))
   print('I choose first and will win on first seeing {} in the list of tosses'.format(me))
   while len(you) != 3 or any(ch not in 'HT' for ch in you) or you == me:
       you = input('What sequence of three Heads/Tails will you win with: ')

else: 

   while len(you) != 3 or any(ch not in 'HT' for ch in you):
       you = input('After you: What sequence of three Heads/Tails will you win with: ')
   me = ('H' if you[1] == 'T' else 'T') + you[:2]
   print('I win on first seeing {} in the list of tosses'.format(me))

print('Rolling:\n ', end=) rolled = while True: 

   rolled += random.choice('HT')
   print(rolled[-1], end=)
   if rolled.endswith(you):
       print('\n  You win!')
       break
   if rolled.endswith(me):
       print('\n  I win!')
       break
   sleep(1)    # For dramatic effect</lang>
Output:
>>> 
After you: What sequence of three Heads/Tails will you win with: TTH
I win on first seeing HTT in the list of tosses
Rolling:
  THHTHHTT
  I win!
>>> ================================ RESTART ================================
>>> 
I choose first and will win on first seeing HHT in the list of tosses
What sequence of three Heads/Tails will you win with: THH
Rolling:
  HTHTHTTTHTTTTTTHH
  You win!
>>>

R

<lang rsplus>#===============================================================

  1. Penney's Game Task from Rosetta Code Wiki
  2. R implementation
  3. ===============================================================

penneysgame <- function() { 

 #---------------------------------------------------------------
 # Who goes first?
 #---------------------------------------------------------------
 
 first <- sample(c("PC", "Human"), 1)
 
 #---------------------------------------------------------------
 # Determine the sequences
 #---------------------------------------------------------------
 
 if (first == "PC") { # PC goes first
   
   pc.seq <- sample(c("H", "T"), 3, replace = TRUE)
   cat(paste("\nI choose first and will win on first seeing", paste(pc.seq, collapse = ""), "in the list of tosses.\n\n"))
   human.seq <- readline("What sequence of three Heads/Tails will you win with: ")
   human.seq <- unlist(strsplit(human.seq, ""))
   
 } else if (first == "Human") { # Player goest first
   
   cat(paste("\nYou can choose your winning sequence first.\n\n"))
   human.seq <- readline("What sequence of three Heads/Tails will you win with: ")
   human.seq <- unlist(strsplit(human.seq, "")) # Split the string into characters
   pc.seq <- c(human.seq[2], human.seq[1:2]) # Append second element at the start
   pc.seq[1] <- ifelse(pc.seq[1] == "H", "T", "H") # Switch first element to get the optimal guess
   cat(paste("\nI win on first seeing", paste(pc.seq, collapse = ""), "in the list of tosses.\n"))
   
 }
 
 #---------------------------------------------------------------
 # Start throwing the coin
 #---------------------------------------------------------------
 
 cat("\nThrowing:\n")
 
 ran.seq <- NULL
 
 while(TRUE) {
   
   ran.seq <- c(ran.seq, sample(c("H", "T"), 1)) # Add a new coin throw to the vector of throws
   
   cat("\n", paste(ran.seq, sep = "", collapse = "")) # Print the sequence thrown so far
   
   if (length(ran.seq) >= 3 && all(tail(ran.seq, 3) == pc.seq)) {
     cat("\n\nI win!\n")
     break
   }
   
   if (length(ran.seq) >= 3 && all(tail(ran.seq, 3) == human.seq)) {
     cat("\n\nYou win!\n")
     break
   }
   
   Sys.sleep(0.5) # Pause for 0.5 seconds
   
 }

} </lang>

Output:

Human first. 

You can choose your winning sequence first.

What sequence of three Heads/Tails will you win with: THH

I win on first seeing TTH in the list of tosses.

Throwing:

 T
 TT
 TTT
 TTTH

I win!

PC first 

I choose first and will win on first seeing THH in the list of tosses.

What sequence of three Heads/Tails will you win with: TTH

Throwing:

 T
 TH
 THT
 THTT
 THTTH

You win!

Racket

This does what's required of it from the task... just don't input anything outside the alphabet "htHT" for the human move.

<lang racket>#lang racket

Penney's Game. Tim Brown 2014-10-15

(define (flip . _) (match (random 2) (0 "H") (1 "T")))

(define (get-human-sequence) ; no sanity checking here! 

 (display "choose your winning sequence of 3 H or T > ")
 (drop-right (drop (string-split (string-upcase (read-line)) "") 1) 1))

(define flips->string (curryr string-join "."))

(define (game-on p1 p2) 

 (printf "~a chooses: ~a. ~a chooses: ~a~%"
         (car p1) (flips->string (cdr p1)) (car p2) (flips->string (cdr p2)))
 (match-define (list (list name.1 p1.1 p1.2 p1.3) (list name.2 p2.1 p2.2 p2.3)) (list p1 p2))
 (let turn ((seq null))
   (match seq
     [(list-rest (== p1.3) (== p1.2) (== p1.1) _) name.1]
     [(list-rest (== p2.3) (== p2.2) (== p2.1) _) name.2]
     [else
      (let* ((flp (flip)) (seq+ (cons flp else)))
        (printf "new-flip: ~a -> ~a~%" flp (flips->string (reverse seq+))) (turn seq+))])))

(define (play-game) 

 (define-values
   (player-1 player-2)
   (match (flip)
     ["H" (printf "Human chooses first: ")
          (define p1 (cons 'Hom-Sap (get-human-sequence)))
          (values p1 (cons 'Computer
                           (match p1
                             [(list _ f1 (and f2 (app (match-lambda ("H" "T") ("T" "H")) ¬f2)) _)
                              (list ¬f2 f1 f2)])))]
     ["T" (printf "Computer chooses first. ")
          (define p1 (cons 'Computer (build-list 3 flip)))
          (printf "~a chooses: ~a~%" (car p1) (flips->string (cdr p1)))
          (values p1 (cons 'Hom-Sap (get-human-sequence)))]))
 (printf "~a wins!~%" (game-on player-1 player-2)))</lang>
Output:

Homo Sapiens Plays First (and wins!)

> (play-game)
Human chooses first: choose your winning sequence of 3 H or T > hth
Hom-Sap chooses: H.T.H. Computer chooses: H.H.T
new-flip: H -> H
new-flip: T -> H.T
new-flip: H -> H.T.H
Hom-Sap wins!

The Computer Plays First (and loses!)

> (play-game)
Computer chooses first. Computer chooses: T.T.T
choose your winning sequence of 3 H or T > htt
Computer chooses: T.T.T. Hom-Sap chooses: H.T.T
new-flip: H -> H
new-flip: H -> H.H
new-flip: H -> H.H.H
new-flip: T -> H.H.H.T
new-flip: H -> H.H.H.T.H
new-flip: T -> H.H.H.T.H.T
new-flip: H -> H.H.H.T.H.T.H
new-flip: T -> H.H.H.T.H.T.H.T
new-flip: H -> H.H.H.T.H.T.H.T.H
new-flip: T -> H.H.H.T.H.T.H.T.H.T
new-flip: T -> H.H.H.T.H.T.H.T.H.T.T
Hom-Sap wins!

(Nail-biting stuff!)

REXX

The REXX program keeps a running score   (number of wins out of so many games played)   as well as
allowing the human to pick the number (length) of the coin toss sequence.

A fair amount of code was added to ensure a valid response from the human player as well as give an informative error message.

The human player is allowed to spell out the   H   or   T   (as heads or tails).

A feature also added was to allow a seed for the   random   BIF to allow repeatability for a game. <lang rexx>/*REXX program plays/simulates Penney's Game, a two-player coin toss sequence game. */ __=copies('─',9) /*literal for eyecatching fence. */ signal on halt /*a clean way out if CLBF quits. */ parse arg # seed . /*obtain optional arguments from the CL*/ if #== | #=="," then #=3 /*Not specified? Then use the default.*/ if datatype(seed,'W') then call random ,,seed /*use seed for RANDOM #s repeatability.*/ wins=0; do games=1 /*simulate a number of Penney's games. */ 

          call game                             /*simulate a single inning of a game.  */
          end   /*games*/                       /*keep at it until  QUIT  or  halt.    */

exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ halt: say; say __ "Penney's Game was halted."; say; exit 13 r: arg ,$; do arg(1); $=$ || random(0,1); end; return $ s: if arg(1)==1 then return arg(3); return word(arg(2) 's',1) /*pluralizer.*/ /*──────────────────────────────────────────────────────────────────────────────────────*/ game: @.=; tosses=@. /*the coin toss sequence so far. */ 

      toss1=r(1)                                      /*result:   0=computer,   1=CBLF.*/
      if \toss1  then call randComp                   /*maybe let the computer go first*/
      if  toss1  then say __ "You win the first toss, so you pick your sequence first."
                 else say __ "The computer won first toss, the pick was: "    @.comp
                      call prompter                   /*get the human's guess from C.L.*/
                      call randComp                   /*get computer's guess if needed.*/
                                                      /*CBLF:  carbon-based life form. */
      say __  "      your pick:"  @.CBLF              /*echo human's pick to terminal. */
      say __  "computer's pick:"  @.comp              /*  "  comp.'s   "   "     "     */
      say                                             /* [↓]  flip the coin 'til a win.*/
            do  flips=1  until pos(@.CBLF,tosses)\==0  |  pos(@.comp,tosses)\==0
            tosses=tosses || translate(r(1),'HT',10)
            end   /*flips*/                           /* [↑]   this is a flipping coin,*/
                                                      /* [↓] series of tosses*/
      say __ "The tossed coin series was: "   tosses
      say
      @@@="won this toss with "   flips   ' coin tosses.'
      if pos(@.CBLF,tosses)\==0  then do;  say __  "You"  @@@;  wins=wins+1;  end
                                 else      say __  "The computer"  @@@
      _=wins;  if _==0  then _='no'
      say __ "You've won"  _  "game"s(wins)  'out of ' games"."
      say;  say copies('╩╦',79%2)'╩';  say
      return

/*──────────────────────────────────────────────────────────────────────────────────────*/ prompter: oops=__ 'Oops! '; a= /*define some handy REXX literals*/ 

         @a_z='ABCDEFG-IJKLMNOPQRS+UVWXYZ'            /*the extraneous alphabetic chars*/
         p=__ 'Pick a sequence of'  #  "coin tosses of  H or T (Heads or Tails) or Quit:"
            do  until  ok;   say;  say p;  pull a     /*uppercase the answer.          */
            if abbrev('QUIT',a,1)  then exit 1        /*the human wants to  quit.      */
            a=space(translate(a,,@a_z',./\;:_'),0)    /*elide extraneous characters.   */
            b=translate(a,10,'HT');    L=length(a)    /*translate ───► bin; get length.*/
            ok=0                                      /*the response is  OK  (so far). */
                select                                /*verify the user response.      */
                when \datatype(b,'B') then say oops "Illegal response."
                when \datatype(a,'M') then say oops "Illegal characters in response."
                when L==0             then say oops "No choice was given."
                when L<#              then say oops "Not enough coin choices."
                when L>#              then say oops "Too many coin choices."
                when a==@.comp        then say oops "You can't choose the computer's choice: " @.comp
                otherwise         ok=1
                end   /*select*/
            end       /*until ok*/
         @.CBLF=a;           @.CBLF!=b                /*we have the human's guess now. */
         return

/*──────────────────────────────────────────────────────────────────────────────────────*/ randComp: if @.comp\== then return /*the computer already has a pick*/ 

         _=@.CBLF!                                    /* [↓] use best-choice algorithm.*/
         if _\==  then g=left((\substr(_, min(2, #), 1))left(_, 1)substr(_, 3), #)
           do  until g\==@.CBLF!;   g=r(#);   end     /*otherwise, generate a choice.  */
         @.comp=translate(g, 'HT', 10)
         return</lang>

output   of a six-game session   (ended by user entering a quit): 

───────── The computer won first toss, the pick was:  HHH

───────── Pick a sequence of 3 coin tosses of  H or T (Heads or Tails) or Quit:
tail tail tails          ◄■■■■■■■■■■■ human's input

─────────       your pick: TTT
───────── computer's pick: HHH

───────── The computer won this toss with  12  coin tosses.

───────── The tossed coin series was:  HHTTHHTHTHHH

───────── You've won no games out of  1.

╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩

───────── You win the first toss, so you pick your sequence first.

───────── Pick a sequence of 3 coin tosses of  H or T (Heads or Tails) or Quit:
h, h, t                  ◄■■■■■■■■■■■ human's input

─────────       your pick: HHT
───────── computer's pick: THT

───────── The computer won this toss with  5  coin tosses.

───────── The tossed coin series was:  TTTHT

───────── You've won no games out of  2.

╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩

───────── The computer won first toss, the pick was:  HHT

───────── Pick a sequence of 3 coin tosses of  H or T (Heads or Tails) or Quit:
heads heads heads        ◄■■■■■■■■■■■ human's input

─────────       your pick: HHH
───────── computer's pick: HHT

───────── The computer won this toss with  3  coin tosses.

───────── The tossed coin series was:  HHT

───────── You've won no games out of  3.

╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩

───────── The computer won first toss, the pick was:  HTH

───────── Pick a sequence of 3 coin tosses of  H or T (Heads or Tails) or Quit:
t t h                    ◄■■■■■■■■■■■ human's input 

─────────       your pick: TTH
───────── computer's pick: HTH

───────── You won this toss with  3  coin tosses.

───────── The tossed coin series was:  TTH

───────── You've won 1 game out of  4.

╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩

───────── You win the first toss, so you pick your sequence first.

───────── Pick a sequence of 3 coin tosses of  H or T (Heads or Tails) or Quit:
t,h,h                    ◄■■■■■■■■■■■ human's input

─────────       your pick: THH
───────── computer's pick: HTH

───────── You won this toss with  4  coin tosses.

───────── The tossed coin series was:  TTHH

───────── You've won 2 games out of  5.

╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩

───────── The computer won first toss, the pick was:  TTH

───────── Pick a sequence of 3 coin tosses of  H or T (Heads or Tails) or Quit:
tth                      ◄■■■■■■■■■■■ human's input
───────── Oops!   You can't choose the computer's choice:  TTH

───────── Pick a sequence of 3 coin tosses of  H or T (Heads or Tails) or Quit:
tht                      ◄■■■■■■■■■■■ human's input

─────────       your pick: THT
───────── computer's pick: TTH

───────── The computer won this toss with  3  coin tosses.

───────── The tossed coin series was:  TTH

───────── You've won 2 games out of  6.

╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩╦╩

───────── You win the first toss, so you pick your sequence first.

───────── Pick a sequence of 3 coin tosses of  H or T (Heads or Tails) or Quit:
quit                     ◄■■■■■■■■■■■ human's input

Ruby

<lang ruby>Toss = [:Heads, :Tails]

def yourChoice 

 puts "Enter your choice (H/T)"
 choice = []
 3.times do
   until (c = $stdin.getc.upcase) == "H" or c == "T"
   end
   choice << (c=="H" ? Toss[0] : Toss[1])
 end
 puts "You chose #{choice.join(' ')}"
 choice

end

loop do 

 puts "\n%s I start, %s you start ..... %s" % [*Toss, coin = Toss.sample]
 if coin == Toss[0]
   myC = Toss.shuffle << Toss.sample
   puts "I chose #{myC.join(' ')}"
   yC = yourChoice
 else
   yC = yourChoice
   myC = Toss - [yC[1]] + yC.first(2)
   puts "I chose #{myC.join(' ')}"
 end
 
 seq = Array.new(3){Toss.sample}
 print seq.join(' ')
 loop do
   puts "\n I win!" or break   if seq == myC
   puts "\n You win!" or break if seq == yC
   seq.push(Toss.sample).shift
   print " #{seq[-1]}"
 end

end</lang>

Output:
Heads I start, Tails you start ..... Tails
Enter your choice (H/T)
THT
You chose Tails Heads Tails
I chose Tails Tails Heads
Heads Tails Heads Heads Tails Tails Tails Heads
 I win!

Heads I start, Tails you start ..... Heads
I chose Heads Heads Heads
Enter your choice (H/T)
THH
You chose Tails Heads Heads
Heads Heads Tails Heads Tails Heads Tails Tails Tails Tails Tails Tails Tails Heads Heads
 You win!

Tcl

Works with: Tcl version 8.6

<lang tcl>package require Tcl 8.6

oo::class create Player { 

   variable who seq seen idx

   constructor {name sequence} {

set who $name set seq $sequence set seen {} set idx end-[expr {[string length $seq] - 1}] 

   }

   method pick {} {

return $seq 

   }

   method name {} {

return $who 

   }

   method match {digit} {

append seen $digit return [expr {[string range $seen $idx end] eq $seq}] 

   }

}

oo::class create HumanPlayer { 

   superclass Player
   constructor {length {otherPlayersSelection ""}} {

fconfigure stdout -buffering none while true { puts -nonewline "What do you pick? (length $length): " if {[gets stdin pick] < 0} exit set pick [regsub -all {[^HT]} [string map {0 H 1 T h H t T} $pick] ""] if {[string length $pick] eq $length} break puts "That's not a legal pick!" } set name "Human" if {[incr ::humans] > 1} {append name " #$::humans"} next $name $pick 

   }

}

oo::class create RobotPlayer { 

   superclass Player
   constructor {length {otherPlayersSelection ""}} {

if {$otherPlayersSelection eq ""} { set pick "" for {set i 0} {$i < $length} {incr i} { append pick [lindex {H T} [expr {int(rand()*2)}]] } } else { if {$length != 3} { error "lengths other than 3 not implemented" } lassign [split $otherPlayersSelection ""] a b c set pick [string cat [string map {H T T H} $b] $a $b] } set name "Robot" if {[incr ::robots] > 1} {append name " #$::robots"} puts "$name picks $pick" next $name $pick 

   }

}

proc game {length args} { 

   puts "Let's play Penney's Game!"

   # instantiate the players
   set picks {}
   set players {}
   while {[llength $args]} {

set idx [expr {int(rand()*[llength $args])}] set p [[lindex $args $idx] new $length {*}$picks] set args [lreplace $args $idx $idx] lappend players $p lappend picks [$p pick] 

   }

   # sanity check
   if {[llength $picks] != [llength [lsort -unique $picks]]} {

puts "Two players picked the same thing; that's illegal" 

   }

   # do the game loop
   while 1 {

set coin [lindex {H T} [expr {int(rand()*2)}]] puts "Coin flip [incr counter] is $coin" foreach p $players { if {[$p match $coin]} { puts "[$p name] has won!" return } } 

   }

}

game 3 HumanPlayer RobotPlayer</lang>

Sample Game:
Let's play Penney's Game!
What do you pick? (length 3): HTH
Robot picks HHT
Coin flip 1 is T
Coin flip 2 is H
Coin flip 3 is T
Coin flip 4 is T
Coin flip 5 is T
Coin flip 6 is H
Coin flip 7 is T
Coin flip 8 is T
Coin flip 9 is H
Coin flip 10 is T
Coin flip 11 is T
Coin flip 12 is T
Coin flip 13 is H
Coin flip 14 is T
Coin flip 15 is T
Coin flip 16 is H
Coin flip 17 is T
Coin flip 18 is T
Coin flip 19 is H
Coin flip 20 is T
Coin flip 21 is H
Human has won!

UNIX Shell

Works with: Bash

<lang sh>#!/bin/bash main() { 

 echo "Penney's Game"
 echo -n "Flipping to see who goes first ... "

 if $(flip) == H ; then
   echo "I do."
   p2=$(choose_sequence)
   echo "I choose: $p2"
 else
   echo "You do."
 fi

 while true; do
   echo "Enter your three-flip sequence:"
   read p1
   case "$p1" in
    "$p2") echo "Sequence must be different from mine";;
    [hHTt][hHtT][hHtT]) break;;
    *) echo "Sequence must be three H's or T's";;
   esac
 done
 p1=$(tr a-z A-Z <<<"$p1")

 if [ -z "$p2" ]; then 
   p2=$(choose_sequence "$p1")
   echo "I choose: $p2"
 fi

 echo
 echo "Here we go.  $p1, you win; $p2, I win."
 flips=

 while true; do
   flip=$(flip)
   echo -n $flip
   flips+=$flip
   while (( ${#flips} > 3 )); do
     flips="${flips#?}"
   done
   case "$flips" in
     *$p1) echo $'\nYou win!'; exit 0;;
     *$p2) echo $'\nI win!'; exit 1;;
   esac
 done

}

choose_sequence() { 

 local result
 if (( $# )); then
   case "$1" in
     ?Hh?) result=T;;
     *) result=H;;
   esac
   result+="${1%?}"
 else
   result=$(flip)$(flip)$(flip)
 fi
 echo "$result"

}

flip() { 

 if (( RANDOM % 2 )); then 
   echo H
 else
   echo T
 fi

}

main "$@"</lang>

Output:

PC first: 

Penney's Game
Flipping to see who goes first ... I do.
I choose: HHT
Enter your three-flip sequence:
THH

Here we go.  THH, you win; HHT, I win.
THH
You win!

Human first: 

penney
Penney's Game
Flipping to see who goes first ... You do.
Enter your three-flip sequence:
HTH
I choose: HHT

Here we go.  HTH, you win; HHT, I win.
HHHT
I win!

zkl

<lang zkl>fcn coinToss{ (0).random(2) and "H" or "T" } // (0).random(2) --> 0<=r<2 reg myBet, yourBet; if(coinToss()=="H"){ // The toss says I go first 

  myBet=(3).pump(String,coinToss);
  println("I bet ",myBet);
  yourBet=ask("Your bet of three (H/T): ")[0,3].toUpper();

}else{ 

  yourBet=ask("Your bet of three (H/T): ")[0,3].toUpper();
  myBet=((yourBet[1]=="H") and "T" or "H") + yourBet[0,2];
  println("I bet ",myBet);

} print("Flipping: "); coins:=""; while(1){ 

  print(toss:=coinToss()); coins=coins + toss;
  if(Void!=coins.find(yourBet)){ println(" You win!"); break; }
  if(Void!=coins.find(myBet))  { println(" I win!"); break; }
  // ignore we both won

}</lang>

Output:
$ zkl bbb
Your bet of three (H/T): tth
I bet HTT
Flipping: HHHHHHTHHTHHHTHTHHHTHTHTT I win!

$ zkl bbb
I bet THT
Your bet of three (H/T): hhh
Flipping: THHH You win!
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