IC210 Lab 6: Viva Las Vegas

Pre-lab homework. Turn in a flowchart OR pseudocode for the following complete program (parts 1 thru 4; you can save part 5 analysis for the lab itself). Your flowchart/pseudocode is to focus on the conceptually difficult parts of the program’s control flow logic (it does NOT have to contain every detail such as all variable declarations). Reminder: All pre-lab homework is due at the beginning of the lab period, and late pre-lab homework will earn a grade of 0.

Executive Summary: You will build a version of the dice game "craps". A detailed explanation of the game comes later. First, however, a note on randomness and computer programs. A key element of any game of chance is the random nature of somthing like rolling the dice. How do we introduce "randomness" into a computer program, which is structured specifically to be "non-random"? Well, the standard library cstdlib has a function called rand which generates "random" numbers. The rand function returns an integer between 0 and RAND_MAX (a number defined in cstdlib that is at least 32,767). The number returned will at least appear to have been randomly chosen in the range (more on that later).

Part 1 : "Let's Roll"

Write a program that simulates the roll of two six-sided die. The program should output the results of 5 rolls of the two die in the following format: 

 
Player rolled 6 + 5 = 11
Player rolled 2 + 6 = 8
Player rolled 3 + 4 = 7
Player rolled 4 + 3 = 7
Player rolled 1 + 5 = 6

To use the rand function, you must include the cstdlib library. The prototype for rand is:

 
int rand();

How to do you transform a random number between 0 and RAND_MAX into a random number from 1 through 6? Use the modulus operator (%) : you figure out the rest!

Part 2 : "Why am I going to Jail?

Run your program from Part 1 three times in succession. What do you note about the output? Nothing random about it! You will be brought up on charges by the Gaming Commission if you implement a "craps" game using this random number generator. The reason for this repeating sequence is not accidental. In order to debug a program that uses a RNG, it may be important to repeat the same sequence. Once the program is debugged, we can "seed" our RNG to create a changing sequence. We use the function srand to "seed" rand. The idea is that the particular sequence of seemingly random numbers rand produces will actually depend on the seed value - different seed values will produce wildly different sequences.

Add to your code from Part 1 the following code: 

int seed;
cout << "Enter a seed value: ";
cin >> seed;
srand(seed);

so that it appears as the first thing in "main". Execute your program three times using different seed values. Your results will be different for each new seed.

Execute your program three times using the same seed value. You will observe the same sequence! Here comes the Gaming Commission again! We do not want to have the user generate the "seed" because output can be predicted based on the seed value.

How can we seed our RNG without input from the user and have unpredictable seed values? Let's use a function from the ctime library. The function call time(0) returns an integer that is the number of seconds ellapsed since 00:00 hours, Jan 1, 1970. This is a continuously changing value that does not repeat, so it makes a great seed value. modify your Part 1 solution by including the ctime function and adding the line 

srand(time(0));

... immediately after "main". Run your program several times. You should no longer notice any predictable patterns in the results. Note: Only seed the random number generator once, typically at the beginning of a program. If you seed it before every call to rand, you'll be resetting the sequence constantly, and it won't look very random.

Part 3 : Craps.

The rules for your game of craps are as follows: If the player rolls a 7 or 11 then the player wins. If the player rolls a 2, 3, or 12 the house wins. The player will continue to roll until either the player or the house wins. Your main program must use a function named "rollDice" (which you'll create) with the following prototype: 

 
int rollDice();

The function rollDice will simulate a roll of two dice, compute the sum of the two dice, and return that sum. Based on the result of rollDice, main will do one of three things: 1) Output "Player Wins!" 2) Output "House Wins!" 3) output "No Winner : Roll again". The program will continue to execute until either the player or the house wins. Sample output:

NOTE: The screenshot above includes “Press any key to continue”.  This is output (and waiting) that is sometimes added by Windows-based compilers.  For this part (and for all parts in this course, unless we say otherwise!) you do NOT have to include this part in your solution.

Part 4 : "You're Fired!"

The owner of the casino, runs analysis on your craps program and sees the odds are stacked in favor of the player. He orders you to implement a version that favors the house. After showing your game to a math professor, the following rules are added to your game.

1.      On the first roll, you win on 7 or 11, and you lose with 2, 3, or 12. Game over.

2.      If the first roll is 4, 5, 6, 8, 9,or 10 then the number rolled becomes your setpoint. You then repeatedly roll the die until you either roll your setpoint for a win or you roll a 2, 3, 7, or 12 for a loss (7 is a loser for the player unless rolled on the first try).

Sample Game:

Part 5 : "Show me the money"

Your program must make "the house" some money, so modify your program of part 4 to add the following functionality.

1.      Ask the player if he wants to play again, and continue to play until the player wants to quit.

2.      The default bet is $5. Track the number of wins for the player and the number of wins for the house. When the player quits, invoke a function (which you create) with the following prototype: 

void showMoney(int pWins, int hWins);

The function accepts two integers (number of wins for player and house). It computes the amount of won or amount owed based on $5 per game and outputs a message telling the user "You won $XX! " or "Pay $XX to the cashier or your legs will be broken!"

GOING BEYOND: If you finish the above portions (requred for lab turn-in) before lab period is finished, attempt the following:

  1. Write a function that takes an integer between 1 and 52 and outputs a card from the standard 52 deck. For instance, value of 1 would go to AH, 2 to 2H, 3 to 3H, etc. Suggested notation: 10H, JH, QH, KH. For other suits: 2C, 2S, 2D, etc. Test your function.
  2. Use your function to randomly generate two cards and output that (2-card) "hand".
  3. Use your above code to play one player blackjack against a dealer. The dealer should always hit until he has at least 17. The goal is to get 21, where jacks, queens, and kings count for 10, and aces for 1 OR 11. For simplicity, start by treatinng aces as always 11. Ask your instructor if you need more details. You'll probably want a function that takes an integer (1-52) and return the "value" of that card.