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Penney's game

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:

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.

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.

11l

Translation of: Python
V first = random:choice([1B, 0B])

V you = ‘’
V me = ‘’
V ht = ‘HT’ // to get round ‘bug in MSVC 2017’[https://developercommunity.visualstudio.com/t/bug-with-operator-in-c/565417]
I first
me = random:sample(Array(‘HT’ * 3), 3).join(‘’)
print(‘I choose first and will win on first seeing #. in the list of tosses’.format(me))
L you.len != 3 | any(you.map(ch -> ch !C :ht)) | you == me
you = input(‘What sequence of three Heads/Tails will you win with: ’)
E
L you.len != 3 | any(you.map(ch -> ch !C :ht))
you = input(‘After you: What sequence of three Heads/Tails will you win with: ’)
me = (I you == ‘T’ {‘H’} E ‘T’)‘’you[0.<2]
print(‘I win on first seeing #. in the list of tosses’.format(me))

print("Rolling:\n ", end' ‘’)
V rolled = ‘’
L
rolled ‘’= random:choice(‘HT’)
print(rolled.last, end' ‘’)
I rolled.ends_with(you)
print("\n You win!")
L.break
I rolled.ends_with(me)
print("\n I win!")
L.break
sleep(1)
Output:
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: THT
Rolling:
THT
You win!

AutoHotkey

Gui, font, s12
loop, 3
Gui, add, button, x+10 h30 w30 vCB%A_Index%
Gui, add, edit, xs w240 R3 vSequence
loop, 3
Gui, add, button, x+10 h30 w30 vHB%A_Index% gHumButton, H
Gui, add, button, xm gToss, toss
Gui, add, button, x+10 gReset, Reset
Gui, show,, Penney's game
CompSeq := HumSeq := Seq := GameEnd := ""

RandomStart:
Random, WhoStarts, 1, 2
if (WhoStarts=1)
gosub, CompButton
return
;-----------------------------------------------
CompButton:
if CompSeq
return
Loop, 3
{
Random, coin, 1, 2
GuiControl,, CB%A_Index%, % coin=1?"H":"T"
CompSeq .= coin=1?"H":"T"
}
return
;-----------------------------------------------
HumButton:
if HumSeq
return
GuiControlGet, B,, % A_GuiControl
GuiControl,, % A_GuiControl, % B="H"?"T":"H"
return
;-----------------------------------------------
Toss:
if GameEnd
return
if !HumSeq
{
loop 3
{
GuiControlGet, B,, HB%A_Index%
HumSeq .= B
}
if (CompSeq = HumSeq)
{
MsgBox, 262160, Penney's game, Human's Selection Has to be different From Computer's Selection`nTry Again
HumSeq := ""
return
}
}
if !CompSeq
{
CompSeq := (SubStr(HumSeq,2,1)="H"?"T":"H") . SubStr(HumSeq,1,2)
loop, Parse, CompSeq
GuiControl,, CB%A_Index%, % A_LoopField
}

Random, coin, 1, 2
Seq .= coin=1?"H":"T"
GuiControl,, Sequence, % seq
if (SubStr(Seq, -2) = HumSeq)
MsgBox % GameEnd := "Human Wins"
else if (SubStr(Seq, -2) = CompSeq)
MsgBox % GameEnd := "Computer Wins"
return
;-----------------------------------------------
Reset:
loop, 3
{
GuiControl,, CB%A_Index%
GuiControl,, HB%A_Index%, H
}
GuiControl,, Sequence
CompSeq := HumSeq := Seq := GameEnd := ""
gosub, RandomStart
return
;-----------------------------------------------

BASIC

BASIC256

Translation of: FreeBASIC

do
valido = TRUE
print chr(10) + "Ingresa una secuencia de 3 opciones, cada una de ellas H o T:";
input " > ", secuencia
secuencia = upper(secuencia)
if length(secuencia) <> 3 then valido = FALSE
if secuencia = computador then print "Pero no la misma que yo..."+ chr(10): valido = FALSE
if valido then
for i = 1 to 3
opcion = mid(secuencia, i, 1)
if opcion <> "H" and opcion <> "T" then valido = FALSE
next i
end if
until valido
end function

function LanzamientoCPU()
secuencia = ""
for i = 1 to 3
opcion = rand
if opcion < .5 then secuencia += "H" else secuencia += "T"
next i
LanzamientoCPU = secuencia
end function

do
cls
print "*** Penney's Game ***" + chr(10)
if rand < .5 then
print "Empiezas... ";
print "Yo gano al ver "; computador; " por primera vez en la lista de lanzamientos..."
else
print "Elijo primero y gano al ver "; computador; " por primera vez en la lista de lanzamientos..."
end if
print: print "Lanzamientos..."
secuencia = ""
winner = FALSE
do
pause 1
if rand <= .5 then
secuencia += "H"
print "H ";
else
print "T ";
secuencia += "T"
end if
if right(secuencia, 3) = jugador then print: print "¡Felicidades! ¡Ganaste!": winner = TRUE
if right(secuencia, 3) = computador then print: print "¡Yo gano!": winner = TRUE
until winner
do
valido = FALSE
print
input "¿Otra partida? (S/N) ", otra
if instr("SsNn", otra) then valido = TRUE
until valido
until upper(otra) = "N"
print "¡Gracias por jugar!"
end

Sinclair ZX81 BASIC

Works with 1k of RAM.

10 IF RND>=.5 THEN GOTO 100
20 PRINT "YOU PICK FIRST."
30 INPUT P\$
40 PRINT "YOU CHOSE ";P\$
50 LET C\$="H"
60 IF P\$(2)="H" THEN LET C\$="T"
70 LET C\$=C\$+P\$( TO 2)
80 PRINT "I CHOOSE ";C\$
90 GOTO 190
100 PRINT "I PICK FIRST."
110 LET C\$=""
120 FOR I=1 TO 3
130 LET C\$=C\$+"H"
140 IF RND>=.5 THEN LET C\$(I)="T"
150 NEXT I
160 PRINT "I CHOOSE ";C\$
170 INPUT P\$
180 PRINT "YOU CHOSE ";P\$
190 LET G\$=""
200 IF RND>=.5 THEN GOTO 230
210 LET G\$=G\$+"H"
220 GOTO 240
230 LET G\$=G\$+"T"
240 PRINT AT 5,0;G\$
250 IF LEN G\$<3 THEN GOTO 200
260 IF G\$(LEN G\$-2 TO )=P\$ THEN GOTO 290
270 IF G\$(LEN G\$-2 TO )=C\$ THEN GOTO 310
280 GOTO 200
290 PRINT "YOU WIN"
300 STOP
310 PRINT "I WIN"
Output:
YOU PICK FIRST.
YOU CHOSE HTH
I CHOOSE  HHT

HTTTHTTTTHHT
I WIN

Batch File

::
::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
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
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

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

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

Heads you pick first, tails I pick first.
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.

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#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;
}

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#

Works with: C sharp version 7
using static System.Console;
using System;

public static class PenneysGame
{
const int pause = 500;
const int N = 3;
static Random rng = new Random();

static int Toss() => rng.Next(2);

static string AsString(this int sequence) {
string s = "";
for (int b = 0b100; b > 0; b >>= 1) {
s += (sequence & b) > 0 ? 'T' : 'H';
}
return s;
}

static int UserInput() {
while (true) {
case ConsoleKey.Escape: return -1;
case ConsoleKey.H: return 0;
case ConsoleKey.T: return 1;
}
Console.Write('\b');
}
}

public static void Main2() {
int yourScore = 0, myScore = 0;
while (true) {
WriteLine(\$"Your score: {yourScore}, My score: {myScore}");
WriteLine("Determining who goes first...");
Sleep(pause);
bool youStart = Toss() == 1;
WriteLine(youStart ? "You go first." : "I go first.");
int yourSequence = 0, mySequence = 0;
if (youStart) {
WriteLine("Choose your sequence of (H)eads and (T)ails (or press Esc to exit)");
int userChoice;
for (int i = 0; i < N; i++) {
if ((userChoice = UserInput()) < 0) return;
yourSequence = (yourSequence << 1) + userChoice;
}
mySequence = ((~yourSequence << 1) & 0b100) | (yourSequence >> 1);
} else {
for (int i = 0; i < N; i++) {
mySequence = (mySequence << 1) + Toss();
}

WriteLine("I chose " + mySequence.AsString());
do {
WriteLine("Choose your sequence of (H)eads and (T)ails (or press Esc to exit)");
int choice;
yourSequence = 0;
for (int i = 0; i < N; i++) {
if ((choice = UserInput()) < 0) return;
yourSequence = (yourSequence << 1) + choice;
}
if (yourSequence == mySequence) {
WriteLine();
WriteLine("You cannot choose the same sequence.");
}
} while (yourSequence == mySequence);
}

WriteLine();
WriteLine(\$"Your sequence: {yourSequence.AsString()}, My sequence: {mySequence.AsString()}");
WriteLine("Tossing...");
int sequence = 0;
for (int i = 0; i < N; i++) {
Sleep(pause);
int toss = Toss();
sequence = (sequence << 1) + toss;
Write(toss > 0 ? 'T' : 'H');
}
while (true) {
if (sequence == yourSequence) {
WriteLine();
WriteLine("You win!");
yourScore++;
break;
} else if (sequence == mySequence) {
WriteLine();
WriteLine("I win!");
myScore++;
break;
}
Sleep(pause);
int toss = Toss();
sequence = ((sequence << 1) + toss) & 0b111;
Write(toss > 0 ? 'T' : 'H');
}
WriteLine("Press a key.");
Clear();
}
}

}

Output:
Your score: 0, My score: 0
Determining who goes first...
I go first.
I chose HHH
Choose your sequence of (H)eads and (T)ails (or press Esc to exit)
thh
Your sequence: THH, My sequence: HHH
Tossing...
HTHTHTHTTHH
You win!
Press a key.

Your score: 2, My score: 0
Determining who goes first...
You go first.
Choose your sequence of (H)eads and (T)ails (or press Esc to exit)
thh
Your sequence: THH, My sequence: TTH
Tossing...
HTTTTH
I win!
Press a key.

C++

#include <time.h>
#include <iostream>
#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 != 'Y' && a != '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 == '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;
}

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

Clojure

(ns penney.core
(:gen-class))

(def tails \T)

(defn flip-coin []
(let [flip (rand-int 2)]
(if (= flip 0) heads tails)))

(defn turn [coin]

(defn first-index [combo coll]
(some #(if (= (second %) combo) (first %)) coll))

(defn find-winner [h c]
(if (< h c)
(do (println "YOU WIN!\n") :human)
(do (println "COMPUTER WINS!\n") :computer)))

(defn flip-off [human comp]
(let [flips (repeatedly flip-coin)
idx-flips (map-indexed vector (partition 3 1 flips))
h (first-index (seq human) idx-flips)
c (first-index (seq comp) idx-flips)]
(println (format "Tosses: %s" (apply str (take (+ 3 (min h c)) flips))))
(find-winner h c)))

(defn valid? [combo]
(if (empty? combo) true (and (= 3 (count combo)) (every? #(or (= heads %) (= tails %)) combo))))

(println "What sequence of 3 Heads/Tails do you choose?")
(if-not (valid? input) (recur) input)))

(defn optimize-against [combo]
(let [mid (nth combo 1)
comp (str (turn mid) (first combo) mid)]
(println (format "Computer chooses %s: " comp)) comp))

(defn initial-move [game]
(let [combo (apply str (repeatedly 3 flip-coin))]
(println "--------------")
(println (format "Current score | CPU: %s, You: %s" (:computer game) (:human game)))
(if (= (:first-player game) tails)
(do
(println "Computer goes first and chooses: " combo)
combo)
(println "YOU get to go first."))))

(defn play-game [game]
(let [c-move (initial-move game)
(if-not (empty? h-move)
(let [winner (flip-off h-move (if (nil? c-move) (optimize-against h-move) c-move))]
(recur (assoc game winner (inc (winner game)) :first-player (flip-coin))))
(println "Thanks for playing!"))))

(defn -main [& args]
(println "Penney's Game.")
(play-game {:first-player (flip-coin)
:human 0, :computer 0}))
Output:
Penney's Game.
--------------
Current score | CPU: 0, You: 0
Computer goes first and chooses:  THT
What sequence of 3 Heads/Tails do you choose?
tth
Tosses: TTH
YOU WIN!

--------------
Current score | CPU: 0, You: 1
YOU get to go first.
What sequence of 3 Heads/Tails do you choose?
tht
Computer chooses TTH:
Tosses: HHHTTH
COMPUTER WINS!

--------------
Current score | CPU: 1, You: 1
YOU get to go first.
What sequence of 3 Heads/Tails do you choose?

Thanks for playing!

Common Lisp

Translation of: UNIX Shell
(setf *random-state* (make-random-state t))

(defparameter *tails* #\T)

(defun main ()
(format t "Penney's Game~%~%")
(format t "Flipping to see who goes first ...")

(setq p2 nil)
(progn (format t " I do.~%")
(setq p2 (choose-random-sequence))
(format t "I choose: ~A~%" p2))
(format t "You do.~%"))

(setq p1 nil)
(loop while (null p1) doing
(format t "Enter your three-flip sequence: ")
(cond ((/= (length p1) 3)
(format t "Sequence must consist of three flips.~%")
(setq p1 nil))
((string= p1 p2)
(format t "Sequence must be different from mine.~%")
(setq p1 nil))
((notevery #'valid? (coerce p1 'list))
(format t "Sequence must be contain only ~A's and ~A's.~%" *heads* *tails*)
(setq p1 nil))))
(format t "You picked: ~A~%" p1)

(if (null p2)
(progn
(setq p2 (choose-optimal-sequence p1))
(format t "I choose: ~A~%" p2)))

(format t "Here we go. ~A, you win; ~A, I win.~%" p1 p2)
(format t "Flips:")
(let ((winner nil)
(flips '()))
(loop while (null winner) doing
(setq flips (cons (flip) flips))
(format t " ~A" (car flips))
(if (>= (length flips) 3)
(let ((trail (coerce (reverse (subseq flips 0 3)) 'string)))
(cond ((string= trail p1) (setq winner "You"))
((string= trail p2) (setq winner "I"))))))
(format t "~&~A win!" winner)))

(defun flip () (nth (random 2 *random-state*) *sides*))

(defun valid? (flip) (not (null (member flip *sides*))))

(defun choose-random-sequence () (coerce (list (flip) (flip) (flip)) 'string))

(defun choose-optimal-sequence (against)
(let* ((opposed (coerce against 'list))
(my-list (list (opposite middle) (car opposed) middle)))
(coerce my-list 'string)))

(main)
Output:

Computer player first:

Penney's Game

Flipping to see who goes first ... I do.
I choose: THH
You picked: TTH
Here we go. TTH, you win; THH, I win.
Flips: T T T H
You win!

Human player first:

Penney's Game

Flipping to see who goes first ...You do.
You picked: HTT
I choose: HHT
Here we go. HTT, you win; HHT, I win.
Flips: H T T
You win!

D

Translation of: Python
void main() {
import std.stdio, std.random, std.algorithm, std.string,

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;
}
} 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;
}
me = (you == '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;
}
}

The output is the same as the Python entry.

Elixir

Translation of: Ruby
defmodule Penney do

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

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) "
IO.puts "You chose: #{Enum.join(choice, " ")}"
choice
end

case IO.getn("") |> String.upcase do
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
Output:
Penney game score  I : 0, You : 0
You win!

Penney game score  I : 0, You : 1
Heads I start, Tails you start ..... Tails
I chose  : Tails Tails Heads
I win!

Penney game score  I : 1, You : 1
Heads I start, Tails you start ..... Tails

Factor

USING: arrays ascii io kernel math prettyprint random sequences
strings ;
IN: rosetta-code.penneys-game

! Generate a random boolean.
: t|f ( -- t/f )
1 random-bits 0 = ;

! Checks whether the sequence chosen by the human is valid.
: valid-input? ( seq -- ? )
[ [ CHAR: H = ] [ CHAR: T = ] bi or ] filter length 3 = ;

! Prompt the human player for a sequence.
: input-seq ( -- seq )
"Please input a 3-long sequence of H or T (heads or tails)."
print "Example: HTH" print "> " write readln >upper >array ;

! Get the human player's input sequence with error checking.
: get-input ( -- seq )
t [ drop input-seq dup valid-input? not ] loop ;

! Add a random coin flip to a vector.
: flip-coin ( vector -- vector' )
t|f CHAR: H CHAR: T ? over push ;

! Generate a random 3-long sequence of coin flips.
: rand-seq ( -- seq )
V{ } clone 3 [ flip-coin ] times ;

! Generate the optimal sequence response to a given sequence.
: optimal ( seq1 -- seq2 )
[ second dup CHAR: H = [ CHAR: T ] [ CHAR: H ] if ]
[ first ] [ second ] tri 3array nip dup
"The computer chose " write >string write "." print ;

! Choose a random sequence for the computer and report what
! was chosen.
: computer-first ( -- seq )
"The computer picks a sequence first and chooses " write
rand-seq dup >string write "." print >array ;

! The human is prompted to choose any sequence with no
! restrictions.
: human-first ( -- seq )
"You get to go first." print get-input ;

! Forbid the player from choosing the same sequence as the
! computer.
: human-second ( cseq -- cseq hseq )
get-input [ 2dup = not ]
[ drop
"You may not choose the same sequence as the computer."
print get-input
] until ;

! Display a message introducing the game.
: welcome ( -- )
"Welcome to Penney's Game. The computer or the player" print
"will be randomly selected to choose a sequence of" print
"three coin tosses. The sequence will be shown to the" print
"opponent, and then he will choose a sequence." print nl
"Then, a coin will be flipped until the sequence" print
"matches the last three coin flips, and a winner" print
"announced." print nl ;

! Check for human victory.
: human-won? ( cseq hseq coin-flips -- ? )
3 tail* >array = nip ;

! Check for computer victory.
: computer-won? ( cseq hseq coin-flips -- ? )
3 tail* >array pick = 2nip ;

! Flip a coin until a victory is detected. Then, inform the
! player who won.
: flip-coins ( cseq hseq -- )
"Flipping coins..." print
rand-seq [ 3dup [ human-won? ] [ computer-won? ] 3bi or ]
[ flip-coin ] until dup >string print human-won?
[ "You won!" print ] [ "The computer won." print ] if ;

! Randomly choose a player to choose their sequence first.
! Then play a full round of Penney's Game.
: start-game ( -- )
welcome t|f [ human-first dup optimal swap ]
[ computer-first human-second ] if flip-coins ;

start-game
Output:
Welcome to Penney's Game. The computer or the player
will be randomly selected to choose a sequence of
three coin tosses. The sequence will be shown to the
opponent, and then he will choose a sequence.

Then, a coin will be flipped until the sequence
matches the last three coin flips, and a winner
announced.

You get to go first.
Please input a 3-long sequence of H or T (heads or tails).
Example: HTH
> car
Please input a 3-long sequence of H or T (heads or tails).
Example: HTH
> htht
Please input a 3-long sequence of H or T (heads or tails).
Example: HTH
> tth
The computer chose HTT.
Flipping coins...
THHTHTHTHHTHHTHHTT
The computer won.

Welcome to Penney's Game. The computer or the player
will be randomly selected to choose a sequence of
three coin tosses. The sequence will be shown to the
opponent, and then he will choose a sequence.

Then, a coin will be flipped until the sequence
matches the last three coin flips, and a winner
announced.

The computer picks a sequence first and chooses HHH.
Please input a 3-long sequence of H or T (heads or tails).
Example: HTH
> hhh
You may not choose the same sequence as the computer.
Please input a 3-long sequence of H or T (heads or tails).
Example: HTH
> hht
Flipping coins...
HHH
The computer won.

FreeBASIC

Translation of: BBC BASIC

Dim As String eleccion
Dim As Byte valido, i
Do
valido = True
Print !"\nIngresa una secuencia de 3 opciones, cada una de ellas H o T:";
Input " > ", secuencia
If Len(secuencia) <> 3 Then valido = False
If valido Then
For i = 1 To 3
eleccion = Mid(Ucase(secuencia), i, 1)
If eleccion <> "H" And eleccion <> "T" Then valido = False
Next
End If
Loop Until valido
End Sub

Function Aleatorio() As String
Dim As Byte eleccion, i
For i = 1 To 3
eleccion = Rnd And 1
Next
End Function

Function Optima(secuencia As String) As String
If Mid(secuencia, 2, 1) = "H" Then
Optima = "T" + Left(secuencia, 2)
Else
Optima = "H" + Left(secuencia, 2)
End If
End Function

Randomize Timer
Dim Shared As String secuencia
Do
Cls
Color 11
Print "*** Penney's Game ***" & Chr(10)
Color 7
Print "Cara eliges primero, cruz yo elijo primero."
Print "Y es... ";
Sleep 300
Dim As Double ht: ht = Rnd(0 - Timer) And 1
If ht Then
Print "­cara!"
Print !"\nYo elijo "; computador; !".\n"
Else
Print "­cruz!"
Print !"\nYo elijo "; computador; !".\n"
End If
Print "Comenzando el juego ..."
secuencia = ""
Do
Sleep 200
Dim As Integer lanzar = Rnd And 1
If lanzar Then
secuencia += "H"
Print "H ";
Else
Print "T ";
secuencia += "T"
End If

If Right(secuencia, 3) = computador Then
Print !"\n­Gan‚!\n"
Else
If Right(secuencia, 3) = jugador Then
End If
End If
Do
valido = False
Input "¨Otra ronda? (S/N) ", otro
If Instr("SYN", Ucase(otro)) Then valido = True
Loop Until valido
Loop Until Ucase(otro) = "N"
Print !"\n­Gracias por jugar!"
Sleep
End

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.Scanln(&inp)
var Ai  int
var user  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==Ai&&user==Ai&&user==Ai{
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  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  int,p int,q int,r int) int{
if(a==p&&a==q&&a==r){
return 1
}else{
return 0
}
}

Output:

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):

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
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:

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=: [email protected] NB. prompt user for input
checkInput=: 'Choose 3 H/Ts' assert (Vals e.~ ]) , 3 = #
getUserSeq=: (] [ checkInput)@[email protected]
choose1st=: Vals {~ 3 [email protected]\$ 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 [email protected]: 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 [email protected]\$ 2
Result=. (Comp,:You) {[email protected]@E."1 Tosses
'Toss sequence is %s' printf < (3 + <./ Result) {. Tosses
echo ('No result';'You win!';'Computer won!') {::~ *-/ Result
)

Usage:

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!

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;
}
}
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

const SLEN = 3

autobet() = randbool(SLEN)
function autobet(ob::BitArray{1})
rlen = length(ob)
2 < rlen || return ~ob
3 < rlen || return [~ob, ob[1:2]]
opt = falses(rlen)
opt = 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)
end
return b
end

Game Setup

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))

Game Play

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

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

Kotlin

// version 1.2.10

import java.util.Random

val rand = Random()

val optimum = mapOf(
"HHH" to "THH", "HHT" to "THH", "HTH" to "HHT", "HTT" to "HHT",
"THH" to "TTH", "THT" to "TTH", "TTH" to "HTT", "TTT" to "HTT"
)

fun getUserSequence(): String {
println("A sequence of three H or T should be entered")
var userSeq: String
do {
}
while (userSeq.length != 3 || userSeq.any { it != 'H' && it != 'T' })
return userSeq
}

fun getComputerSequence(userSeq: String = ""): String {
val compSeq = if(userSeq == "")
String(CharArray(3) { if (rand.nextInt(2) == 0) 'T' else 'H' })
else
optimum[userSeq]!!
println("Computer's sequence: \$compSeq")
return compSeq
}

fun main(args: Array<String>) {
var userSeq: String
var compSeq: String
val r = rand.nextInt(2)
if (r == 0) {
println("You go first")
userSeq = getUserSequence()
println()
compSeq = getComputerSequence(userSeq)
}
else {
println("Computer goes first")
compSeq = getComputerSequence()
println()
userSeq = getUserSequence()
}

println()
val coins = StringBuilder()
while (true) {
val coin = if (rand.nextInt(2) == 0) 'H' else 'T'
coins.append(coin)
println("Coins flipped: \$coins")
val len = coins.length
if (len >= 3) {
val seq = coins.substring(len - 3, len)
if (seq == userSeq) {
println("\nYou win!")
return
}
else if (seq == compSeq) {
println("\nComputer wins!")
return
}
}
Thread.sleep(2000) // wait two seconds for next flip
}
}

Sample game where computer goes first:

Computer goes first
Computer's sequence: HTT

A sequence of three H or T should be entered

Coins flipped: H
Coins flipped: HH
Coins flipped: HHT

You win!

Sample game where user goes first:

You go first
A sequence of three H or T should be entered

Computer's sequence: HHT

Coins flipped: T
Coins flipped: TT
Coins flipped: TTT
Coins flipped: TTTT
Coins flipped: TTTTH
Coins flipped: TTTTHT
Coins flipped: TTTTHTH

You win!

Lua

function penny_game()
local player, computer = "", ""
function player_choose()
io.write( "Enter your sequence of three H and/or T: " )
if #t > 3 then t = t:sub( 1, 3 )
elseif #t < 3 then return ""
end

for i = 1, 3 do
c = t:sub( i, i )
if c ~= "T" and c ~= "H" then
print( "Just H's and T's!" )
return ""
end
end
return t
end
function computer_choose()
local t = ""
if #player > 0 then
if player:sub( 2, 2 ) == "T" then
t = "H"
else
t = "T";
end
t = t .. player:sub( 1, 2 )
else
for i = 1, 3 do
if math.random( 2 ) == 1 then
t = t .. "H"
else
t = t .. "T"
end
end
end
return t
end
if math.random( 2 ) == 1 then
computer = computer_choose()
io.write( "My sequence is: " .. computer .. "\n" )
while( true ) do
player = player_choose()
if player:len() == 3 then break end
end
else
while( true ) do
player = player_choose()
if player:len() == 3 then break end
end
computer = computer_choose()
io.write( "My sequence is: " .. computer .. "\n" )
end
local coin, i = "", 1
while( true ) do
if math.random( 2 ) == 1 then
coin = coin .. "T"
io.write( "T" )
else
coin = coin .. "H"
io.write( "H" )
end
if #coin > 2 then
local seq = coin:sub( i, i + 2 )
i = i + 1
if seq == player then
print( "\nPlayer WINS!!!" )
return 1
elseif seq == computer then
print( "\nComputer WINS!!!" )
return -1
end
end
end
end
math.randomseed( os.time() )
local cpu, user = 0, 0
repeat
r = penny_game()
if r > 0 then
user = user + 1
else
cpu = cpu + 1
end
print( "Player: " .. user .. " CPU: " .. cpu )
io.write( "Play again (Y/N)? " )
until( r == "N" or r == "n" )

Output:
>lua -e "io.stdout:setvbuf 'no'" "penny.lua"
My sequence is: TTH
Enter your sequence of three H and/or T: HHT
TTTTH
Computer WINS!!!
Player: 0 CPU: 1
Play again (Y/N)? y
Enter your sequence of three H and/or T: HTH
My sequence is: HHT
THTTHTH
Player WINS!!!
Player: 1 CPU: 1
Play again (Y/N)? y
My sequence is: HHH
Enter your sequence of three H and/or T: TTH
HTTHHTH
Player WINS!!!
Player: 2 CPU: 1
Play again (Y/N)? n
>Exit code: 0

MiniScript

randomTorH = function()
if rnd < 0.5 then return "T" else return "H"
end function

if rnd < 0.5 then
playerSeq = input("Input your sequence (e.g. HTH): ").upper
if playerSeq == "T" then compSeq = "H" else compSeq = "T"
compSeq = compSeq + playerSeq[:2]
print "I choose: " + compSeq
else
compSeq = randomTorH + randomTorH + randomTorH
print "I choose: " + compSeq
playerSeq = input("Input your sequence (e.g. HTH): ").upper
end if

print "Here we go..."
seq = ""
while true
flip = randomTorH
print flip
seq = seq + flip
if seq[-3:] == playerSeq then
print "You win!"
break
else if seq[-3:] == compSeq then
print "I win!"
break
end if
wait
end while
Output:
Input your sequence (e.g. HTH): HTH
I choose: HHT
Here we go...
T
H
T
H
You win!
I choose: TTH
THH
Here we go...
H
T
T
T
T
H
I win!

Nim

Translation of: Python
import os, random, sequtils, strutils

randomize()

let first = sample([false, true])

var you, me = ""
if first:
me = newSeqWith(3, sample("HT")).join()
echo "I choose first and will win on first seeing \$# in the list of tosses." % me
while you.len != 3 or not allCharsInSet(you, {'H', 'T'}) or you == me:
stdout.write "What sequence of three Heads/Tails will you win with? "
else:
while you.len != 3 or not allCharsInSet(you, {'H', 'T'}):
echo "After you: what sequence of three Heads/Tails will you win with? "
me = (if you == 'T': 'H' else: 'T') & you[0..1]
echo "I win on first seeing \$# in the list of tosses" % me

var rolled = ""
stdout.write "Rolling:\n "
while true:
stdout.write rolled[^1]
stdout.flushFile()
if rolled.endsWith(you):
echo "\n You win!"
break
elif rolled.endsWith(me):
echo "\n I win!"
break
sleep(1000)
Output:
After you: what sequence of three Heads/Tails will you win with?
HTH
I win on first seeing HHT in the list of tosses
Rolling:
TTHTTTTHHT
I win!

Pascal

PROGRAM Penney;

TYPE
Sequence = array [1..3] of CoinToss;
Player = record
bet: Sequence;
score: integer;
end;

VAR
Human, Computer: Player;
Rounds, Count: integer;

Function TossCoin: CoinToss;
{ Returns heads or tails at random }
Begin
if random(2) = 1 then TossCoin := Heads
else TossCoin := tails
End;

Procedure PutToss(toss: CoinToss);
{ Outputs heads or tails as a letter }
Begin
if toss = heads then write('H')
else write('T')
End;

Function GetToss: CoinToss;
{ Reads H or T from the keyboard in either lettercase }
var c: char;
Begin
{ Keep reading characters until we get an appropriate letter }
repeat read(c) until c in ['H', 'h', 'T', 't'];
{ Interpret the letter }
if c in ['H', 'h'] then GetToss := heads
else GetToss := tails
End;

Procedure ShowSequence(tosses: Sequence);
{ Outputs three coin tosses at once }
Var
i: integer;
Begin
for i := 1 to 3 do PutToss(tosses[i])
End;

{ Accepts three coin tosses from the keyboard }
Var i: integer;
Begin
{ Get the 3 letters }
for i := 1 to 3 do tosses[i] := GetToss;
{ Ignore the rest of the line }
End;

Function Optimum(opponent: Sequence): Sequence;
{ Generates the optimum sequence against an opponent }
Begin
case opponent of
end;
Optimum := opponent;
Optimum := opponent
End;

Function RandomSequence: Sequence;
{ Generates three random coin tosses }
Var
i: integer;
Begin
for i := 1 to 3 do RandomSequence[i] := TossCoin
End;

Function Match(first, second: Sequence): Boolean;
{ Detects whether a sequence of tosses matches another }
Var
different: boolean;
i: integer;
Begin
different := false;
i := 1;
while (i <= 3) and not different do begin
if not (first[i] = second[i]) then different := true;
i := i + 1
end;
Match := not different
End;

Procedure PlayRound(var human, computer: Player);
{ Shows coin tosses and announces the winner }
Var
{ We only ever need to store the 3 most recent tosses in memory. }
tosses: Sequence;
Begin
write('Tossing the coin: ');
tosses := RandomSequence;
ShowSequence(tosses);
{ Keep tossing the coin until there is a winner. }
while not (Match(human.bet, tosses) or Match(computer.bet, tosses)) do begin
tosses := tosses;
tosses := tosses;
tosses := TossCoin;
PutToss(tosses)
end;
{ Update the winner's score and announce the winner }
writeln;
writeln;
if Match(human.bet, tosses) then begin
writeln('Congratulations! You won this round.');
human.score := human.score + 1;
writeln('Your new score is ', human.score, '.')
end
else begin
writeln('Yay, I won this round!');
computer.score := computer.score + 1;
writeln('My new score is ', computer.score, '.')
end
End;

{ Main Algorithm }

BEGIN

{ Welcome the player }
writeln('Welcome to Penney''s game!');
writeln;
write('How many rounds would you like to play? ');
writeln;
writeln('Ok, let''s play ', Rounds, ' rounds.');

{ Start the game }
randomize;
Human.score := 0;
Computer.score := 0;

for Count := 1 to Rounds do begin

writeln;
writeln('*** Round #', Count, ' ***');
writeln;

{ Choose someone randomly to pick the first sequence }
if TossCoin = heads then begin
write('I''ll pick first this time.');
Computer.bet := RandomSequence;
write(' My sequence is ');
ShowSequence(Computer.bet);
writeln('.');
repeat
write('What sequence do you want? ');
if Match(Human.bet, Computer.bet) then
writeln('Hey, that''s my sequence! Think for yourself!')
until not Match(Human.bet, Computer.bet);
ShowSequence(Human.bet);
writeln(', huh? Sounds ok to me.')
end
else begin
write('You pick first this time. Enter 3 letters H or T: ');
Computer.bet := Optimum(Human.bet);
write('Ok, so you picked ');
ShowSequence(Human.bet);
writeln;
write('My sequence will be ');
ShowSequence(Computer.bet);
writeln
end;

{ Then we can actually play the round }
writeln('Let''s go!');
writeln;
PlayRound(Human, Computer);
writeln;
writeln('Press ENTER to go on...');

end;

{ All the rounds are finished; time to decide who won }
writeln;
writeln('*** End Result ***');
writeln;
if Human.score > Computer.score then writeln('Congratulations! You won!')
else if Computer.score > Human.score then writeln('Hooray! I won')
else writeln('Cool, we tied.');
writeln;
writeln('Press ENTER to finish.');

END.
Output:
Welcome to Penney's game!

How many rounds would you like to play?  3

Ok, let's play 3 rounds.

*** Round #1 ***

I'll pick first this time. My sequence is TTH.
What sequence do you want? H tt
HTT, huh? Sounds ok to me.
Let's go!

Tossing the coin: HHHHTHHHHHHTHHHHTHHTHTHTT

Congratulations! You won this round.

Press ENTER to go on...

*** Round #2 ***

I'll pick first this time. My sequence is THT.
What sequence do you want? tth
TTH, huh? Sounds ok to me.
Let's go!

Tossing the coin: THT

Yay, I won this round!
My new score is 1.

Press ENTER to go on...

*** Round #3 ***

You pick first this time. Enter 3 letters H or T: h t h
Ok, so you picked HTH
My sequence will be HHT
Let's go!

Tossing the coin: HHT

Yay, I won this round!
My new score is 2.

Press ENTER to go on...

*** End Result ***

Hooray! I won

Press ENTER to finish.

Perl

#!usr/bin/perl
use 5.020;
use strict;
use warnings;

#Choose who goes first
binaryRand() == 0 ? flipCoin(userFirst()) : flipCoin(compFirst());

#Return a randomly generated 1 or 0
sub binaryRand
{
return int(rand(2));
}
#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";
}
}

#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;
}

#Returns an array with two elements:  user's seq,  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;
}

#Returns an array with two elements:  user's seq,  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;
}

#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;
}
}
}

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!

Phix

Translation of: C

Robert's robot's name is Robort.

function trio(integer pick)
return substitute_all(sprintf("%03b",pick),"10","HT")
end function

function getuser(integer bot)
integer user
while 1 do
user = 8 -- (a bit that clears after 3 shifts)
printf(1,"Enter your sequence of 3 (H/T):");
while user>7 do
integer c = upper(wait_key())
if c=#1B then abort(0) end if -- (Escape)
if find(c,"HT") then
puts(1,c)
user = and_bits(user*2+(c='H'),0b111111)
end if
end while
if user!=bot then exit end if
printf(1,"\nYou may not pick the same as Robort!\n")
end while
printf(1,"\n")
return user
end function

function getbot(int user)
int bot = iff(user=-1?rand(8)-1
:4-and_bits(user,2)*2+floor(user/2))
printf(1,"Robort picks %s\n", {trio(bot)})
return bot
end function

function rungame(integer user, bot)
/* We only need to store the last 3 tosses, as 0..7 */
int last3 = rand(8)-1

printf(1,"Rolling: %s",{trio(last3)})
while 1 do
if user=last3 then
printf(1,"\nUser wins!\n")
return 1
elsif bot=last3 then
printf(1,"\nRobort wins!\n")
return 0
end if
last3 = and_bits(last3,3)*2+(rand(2)=1)
printf(1,"%c", iff(and_bits(last3,1) ? 'H' : 'T'))
sleep(0.5)
end while
end function

procedure main()
integer playerwins = 0,
totalgames = 0,
robortwins = 0

/* Just use ctrl-c or Escape to exit */
while 1 do
integer user = -1,
bot = -1

printf(1,"\n")
if rand(2)=1 then
bot = getbot(-1)
user = getuser(bot)
else
user = getuser(-1)
bot = getbot(user)
end if

playerwins += rungame(user, bot)
totalgames += 1
robortwins = totalgames-playerwins

printf(1,"Robort:%d You:%d out of %d games\n",
{robortwins, playerwins, totalgames})
printf(1,"==================================\n")
end while

end procedure
main()
Output:
Robort picks TTT
Enter your sequence of 3 (H/T):TTT
You may not pick the same as Robort!
Enter your sequence of 3 (H/T):HHH
Rolling: HTTT
Robort wins!
Robort:1  You:0  out of 1 games
==================================

Enter your sequence of 3 (H/T):HTH
Robort picks HHT
Rolling: THTTTHHHHHHT
Robort wins!
Robort:2  You:0  out of 2 games
==================================

Enter your sequence of 3 (H/T):TTH
Robort picks HTT
Rolling: THTT
Robort wins!
Robort:3  You:0  out of 3 games
==================================

Enter your sequence of 3 (H/T):HTH
Robort picks HHT
Rolling: TTHHHHHHT
Robort wins!
Robort:4  You:0  out of 4 games
==================================

Enter your sequence of 3 (H/T):HHT
Robort picks THH
Rolling: TTHH
Robort wins!
Robort:5  You:0  out of 5 games
==================================

Enter your sequence of 3 (H/T):THH
Robort picks TTH
Rolling: THH
User wins!
Robort:5  You:1  out of 6 games
==================================

PicoLisp

(seed (in "/dev/urandom" (rd 8)))

(setq *S (list 0 0))

(de toss (N)
(make
(do N
(link (if (rand T) "T" "H")) ) ) )

(de comp (A Lst)
(or
(for ((I . L) Lst (cddr L) (cdr L))
(T (fully = A L) I) )
T ) )

(de score NIL
(prinl)
(prinl "Total score:")
(prinl "^Iuser: " (car *S))
(prinl "^Icomp: " (cadr *S)) )

(de play NIL
(let (C (toss 3) Lst (toss (rand 5 12)) U)
(prinl)
(prin "Select toss: ")
(setq U (in NIL (skip) (line)))
(prinl "Comp toss: " C)
(prinl "Toss: " Lst)
(setq @ (comp U Lst) @@ (comp C Lst) )
(cond
((< @ @@) (prinl "User win.") (inc *S))
((> @ @@) (prinl "Comp win.") (inc (cdr *S)))
(T (prinl "Draw, lets play again.")) )
(score) ) )

(de go NIL
(loop
(play)
(T
(prog
(prinl)
(prin "Want play again? Y/N: ")
(= "N" (uppc (in NIL (char)))) ) ) ) )

(go)
Output:
Select toss: HTH
Comp toss: THT
Toss: HHTHTTHT
User win.

Total score:
user: 1
comp: 0

Want play again? Y/N: y

Select toss: HHH
Comp toss: HTH
Toss: THHHTTHTHHH
User win.

Total score:
user: 2
comp: 0

Want play again? Y/N: y

Select toss: TTT
Comp toss: THH
Toss: TTHTTHHHHTH
Comp win.

Total score:
user: 2
comp: 1

Want play again? Y/N: n

Prolog

play :- rand1(R), game(R).

game(h) :-
response(P,C), format('I am choosing '), maplist(writec, C), nl,
rand3(R), maplist(writec,R),
roll(P, C, R).

game(t) :-
rand3(C),
format('I am choosing '), maplist(writec, C), nl,
player_move(P),
rand3(R), maplist(writec, R),
roll(P, C, R).

player_move([P1,P2,P3]) :-
maplist(char_code,[P1,P2,P3],Codes).

roll(P, _, P) :- format('~nYou Win!~n'), !.
roll(_, C, C) :- format('~nI Win!~n'), !.

roll(P, C, [_,A,B]) :-
rand1(R),
coin_s(R,S),
write(S),
roll(P,C,[A,B,R]).

response([A,B,_], [C,A,B]) :- opp(A,C).

writec(A) :- coin_s(A,A1), write(A1).
rand1(R) :- random(V), round(V,I), coin(I,R).
rand3([R1,R2,R3]) :- rand1(R1), rand1(R2), rand1(R3).

coin(0,h). coin(1,t).
coin_s(h, 'H'). coin_s(t, 'T').
opp(h, t). opp(t, h).

Output:

?- play.
I am choosing HTT
|: tth
HHTHHHHHHHHTHHHHTHTHTHTHTHHTT
I Win!
true.

?- play.
|: hht
I am choosing THH
TTHTHH
I Win!

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 == '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
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

#===============================================================
# Penney's Game Task from Rosetta Code Wiki
# R implementation
#===============================================================

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, human.seq[1:2]) # Append second element at the start
pc.seq <- ifelse(pc.seq == "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

}
}

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
;; 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)))
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!)

Raku

(formerly Perl 6)

Works with: Rakudo version 2018.02
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 '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), |@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 "\$_ ";
}
}
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...
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
OK!
You feeling lucky?
Here we go!
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!
Hah, I win, and you lose!
Wanna play again? n

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.

/*REXX program plays/simulates  Penney's Game,  a  two─player  coin toss sequence game. */
__= copies('─', 9) /*literal for eye─catching 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(100, 9991) // 2; end; return \$
s: if arg(1)==1 then return arg(3); return word(arg(2) 's',1) /*pluralizer.*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
game: @.=; [email protected]. /*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 [email protected].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\[email protected].CBLF!; g= r(#); end /*otherwise, generate a choice. */
@.comp= translate(g, 'HT', 10)
return
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

───────── 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

───────── 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:

───────── 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

───────── 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

───────── 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

───────── 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

def yourChoice
choice = []
3.times do
until (c = \$stdin.getc.upcase) == "H" or c == "T"
end
choice << (c=="H" ? Toss : Toss)
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
myC = Toss.shuffle << Toss.sample
puts "I chose #{myC.join(' ')}"
yC = yourChoice
else
yC = yourChoice
myC = Toss - [yC] + 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
Output:
Heads I start, Tails you start ..... Tails
THT
I win!

THH
You win!

Rust

extern crate rand;

use std::io::{stdin, stdout, Write};
use std::time::Duration;

use rand::Rng;

fn toss_coin<R: Rng>(rng: &mut R, print: bool) -> char {
let c = if rng.gen() { 'H' } else { 'T' };
if print {
print!("{}", c);
stdout().flush().expect("Could not flush stdout");
}
c
}

fn gen_sequence<R: Rng>(rng: &mut R, seed: Option<&str>) -> String {
let mut seq = String::new();
match seed {
Some(s) => {
let mut iter = s.chars();
let c0 = iter.next().unwrap();
let next = if c0 == 'H' { 'T' } else { 'H' };
seq.push(next);
seq.push(c0);
seq.push(iter.next().unwrap());
}
None => {
for _ in 0..3 {
seq.push(toss_coin(rng, false))
}
}
}
seq
}

fn read_sequence(used_seq: Option<&str>) -> String {
let mut seq = String::new();
loop {
seq.clear();
println!("Please, enter sequence of 3 coins: H (heads) or T (tails): ");
seq = seq.trim().to_uppercase();
// do the cheapest test first
if seq.len() == 3
&& seq.chars().all(|c| c == 'H' || c == 'T')
&& seq != used_seq.unwrap_or("")
{
return seq;
}

}
}

fn main() {

println!("--Penney's game--");
loop {
let useq: String;
let aiseq: String;
if rng.gen::<bool>() {
println!("You choose first!");
aiseq = gen_sequence(&mut rng, Some(&useq));
println!("My sequence: {}", aiseq);
} else {
println!("I choose first!");
aiseq = gen_sequence(&mut rng, None);
println!("My sequence: {}", aiseq);
}
println!("Tossing coins...");
let mut coins = String::new();
for _ in 0..2 {
// toss first 2 coins
coins.push(toss_coin(&mut rng, true));
}
loop {
coins.push(toss_coin(&mut rng, true));
if coins.contains(&useq) {
println!("\nYou win!");
break;
}
if coins.contains(&aiseq) {
println!("\nI win!");
break;
}
}

println!(" Play again? 'Y' to play, 'Q' to exit.");
let mut input = String::new();
match input.trim_start().chars().next().unwrap() {
'Y' | 'y' => continue,
_ => break,
}
}
}

Output:
--Penney's game--
You choose first!
hht
My sequence: THH
Tossing coins...
TTTTHTTHTHTHTTTHH
I win!
Play again? 'Y' to play, 'Q' to exit.

Tcl

Works with: Tcl version 8.6
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
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
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
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
#!/bin/bash
main() {
printf \$'Penney\'s Game\n\n'
printf 'Flipping to see who goes first ... '

if [[ \$(flip) == H ]]; then
printf 'I do.\n'
p2=\$(choose_sequence)
printf 'I choose: %s\n' "\$p2"
else
printf 'You do.\n'
fi

while true; do
p1=\$(tr a-z A-Z <<<"\$p1")
case "\$p1" in
"\$p2") printf 'Sequence must be different from mine\n';;
[HT][HT][HT]) break;;
*) printf \$'Sequence must be three H\'s or T\'s\n';;
esac
done

if [ -z "\$p2" ]; then
p2=\$(choose_sequence "\$p1")
printf 'I choose: %s\n' "\$p2"
fi

printf '\nHere we go.  %s, you win; %s, I win.\n' "\$p1" "\$p2"
printf 'Flips:'

flips=
while true; do
flip=\$(flip)
printf ' %s' "\$flip"
flips+=\$flip
case "\$flips" in
*\$p1) printf \$'\nYou win!\n'; exit 0;;
*\$p2) printf \$'\nI win!\n'; 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
printf '%s\n' "\$result"
}

flip() {
if (( RANDOM % 2 )); then
printf '%s\n' H
else
printf '%s\n' T
fi
}

main "[email protected]"

Output:

PC first:

Penney's Game
Flipping to see who goes first ... I do.
I choose: HHT
THH

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

Human first:

Penney's Game

Flipping to see who goes first ... I do.
I choose: HHH

Here we go.  THH, you win; HHH, I win.
Flips: H H T H H
You win!

Human first:

Penney's Game

Flipping to see who goes first ... You do.
I choose: TTH

Here we go.  THH, you win; TTH, I win.
Flips: H H T T T H
I win!

VBA

Option Explicit

Private Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long)
Private Const HT As String = "H T"

Public Sub PenneysGame()
Dim S\$, YourSeq\$, ComputeSeq\$, i&, Seq\$, WhoWin\$, flag As Boolean

Do
S = WhoWillBeFirst(Choice("Who will be first"))
If S = "ABORT" Then Exit Do
Debug.Print S; " start"
If YourSeq Like "*ABORT*" Then Exit Do
Debug.Print "Your sequence : " & YourSeq
ComputeSeq = vbNullString
For i = 1 To 3
ComputeSeq = ComputeSeq & Random
Next i
Debug.Print "Computer sequence : " & ComputeSeq
Seq = vbNullString
Do
Seq = Seq & Random
Debug.Print Seq
Sleep 1000
Loop While Not Winner(ComputeSeq, YourSeq, Seq, WhoWin)
Debug.Print WhoWin; " win"
If MsgBox(WhoWin & " win" & vbCrLf & "Play again?", vbYesNo) = vbNo Then flag = True
Debug.Print ""
Loop While Not flag
Debug.Print "Game over"
End Sub

Private Function WhoWillBeFirst(YourChoice As String) As String
Dim S\$
S = Random
Select Case YourChoice
Case "ABORT": WhoWillBeFirst = YourChoice
Case Else:
WhoWillBeFirst = IIf(S = YourChoice, "You", "Computer")
End Select
End Function

Private Function Choice(Title As String, Optional Seq As Integer) As String
Dim S\$, i&, t\$
If Seq = 0 Then Seq = 1
t = Title
For i = 1 To Seq
S = vbNullString
Do
S = InputBox("Choose between H or T : ", t)
If StrPtr(S) = 0 Then S = "Abort"
S = UCase(S)
Loop While S <> "H" And S <> "T" And S <> "ABORT"
Choice = Choice & S
t = Title & " " & Choice
If Choice Like "*ABORT*" Then Exit For
Next i
End Function

Private Function Random() As String
Randomize Timer
Random = Split(HT, " ")(CInt(Rnd))
End Function

Private Function Winner(Cs\$, Ys\$, S\$, W\$) As Boolean
If Len(S) < 3 Then
Winner = False
Else
If Right(S, 3) = Cs And Right(S, 3) = Ys Then
Winner = True
W = "Computer & you"
ElseIf Right(S, 3) = Cs And Right(S, 3) <> Ys Then
Winner = True
W = "Computer"
ElseIf Right(S, 3) = Ys And Right(S, 3) <> Cs Then
Winner = True
W = "You"
End If
End If
End Function
Output:
You start
Computer sequence : TTH
H
HT
HTT
HTTH
Computer win

You start
Computer sequence : HHH
T
TT
TTT
TTTH
You win

Game over

Wren

Translation of: Kotlin
Library: Wren-str
import "random" for Random
import "io" for Stdin, Stdout
import "timer" for Timer
import "/str" for Str

var rand = Random.new()

var optimum = {
"HHH": "THH", "HHT": "THH", "HTH": "HHT", "HTT": "HHT",
"THH": "TTH", "THT": "TTH", "TTH": "HTT", "TTT": "HTT"
}

var getUserSequence = Fn.new {
System.print("A sequence of three H or T should be entered")
var userSeq
while (true) {
Stdout.flush()
if (userSeq.count == 3 && userSeq.all { |c| c == "H" || c == "T" }) break
}
return userSeq
}

var getComputerSequence = Fn.new { |userSeq|
var compSeq
if (userSeq == "") {
var chars = List.filled(3, null)
for (i in 0..2) chars[i] = (rand.int(2) == 0) ? "T" : "H"
compSeq = chars.join()
} else {
compSeq = optimum[userSeq]
}
System.print("Computer's sequence: %(compSeq)")
return compSeq
}

var userSeq
var compSeq
var r = rand.int(2)
if (r == 0) {
System.print("You go first")
userSeq = getUserSequence.call()
System.print()
compSeq = getComputerSequence.call(userSeq)
} else {
System.print("Computer goes first")
compSeq = getComputerSequence.call("")
System.print()
userSeq = getUserSequence.call()
}
System.print()
var coins = ""
while (true) {
var coin = (rand.int(2) == 0) ? "H" : "T"
coins = coins + coin
System.print("Coins flipped: %(coins)")
var len = coins.count
if (len >= 3) {
var seq = coins[len-3...len]
if (seq == userSeq) {
System.print("\nYou win!")
return
} else if (seq == compSeq) {
System.print("\nCompter wins!")
return
}
}
Timer.sleep(2000) // wait two seconds for next flip
}
Output:

Sample game where computer goes first:

Computer goes first
Computer's sequence: HHH

A sequence of three H or T should be entered

Coins flipped: H
Coins flipped: HH
Coins flipped: HHH

Compter wins!

Sample game where user goes first:

You go first
A sequence of three H or T should be entered

Computer's sequence: HTT

Coins flipped: H
Coins flipped: HH
Coins flipped: HHH
Coins flipped: HHHT
Coins flipped: HHHTT

Compter wins!

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);
}else{
myBet=((yourBet=="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
}
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!