Task: Penney's game
C: #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':
                
                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) {
        
        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);
    
    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)
{
    
    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;

    
    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;
}

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[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;
}