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;
}

VB: 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"
        YourSeq = Choice("Your sequence", 3)
        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