Lab 6: It's all fun and games

Released: 11:59 PM Sunday, July 5th, 2020.

Due: Check project 2 for deadline.

In this lab, you will finish the implementation of the second project.

This lab is Part 3 for the second project, read the project description again if you need to jog your memory.

This time you will need to submit your final project work to be graded! Check project 2 description for deadline and submission instructions!.

If you haven’t yet, try running the trick with actual playing cards (or just cut 21 pieces of paper and draw some numbers in them :). This can provide a bit of insight into the trick! And thus how it is implemented.

Now the exercise!

Using your lab 5 implementation, add a couple more functions to complete your game.

As before, my advice is to work with numbers until you are ready for the final version. But then, you can just replace in an array of cards. Here is the one I used, if you want to copy-paste it into your code :)

static String[] hand = {"♠A", "♢2", "♡3", "♠4", "♡5", "♠6", "♠7", "♠8", "♡9", "♠Q", "♠J", "♡Q", "♠K", "♣A", "♣2", "♣3", "♢4", "♣5", "♢6", "♣7", "♢8"};

Note: You will have to change the type of your arrays from int to String. But it shouldn’t have a huge impact on the remaining code.

The final assignment for this project is to collect the cards from the table (your 3 columnX arrays) back into the magician’s hand (your hand array). Adjust the names if you named them differently :)

Small recap

When collecting the cards from the table you want to collect the columns in such a way that the column with the player’s card is collected second. E.g.

Hi Dave, where is your card?
Hi HAL, it's in column 1.

Then there are 2 ways of collecting the cards from the table:

1. Columns 2, 1, 3
2. Columns 3, 1, 2

This means that the first and last columns don’t really matter, as long as the second column is the one the user selected.

Implementation suggestion 1

When developing a function, it is a good thing to test it independently of the remaining code. Otherwise, bugs in another bit of code may creep into the execution and make finding mistakes difficult. So my advice, is to ONLY execute the function you are about to implement, not the whole game (ask user for input, place cards in table and ONLY THEN collect them). Instead, initialize your 3 column variables as a sequence of numbers and run your function. E.g.:

static String[] column1 = {1,2,3,4,5,6,7};
static String[] column2 = {8,9,10,11,12,13,14};
static String[] column3 = {15,16,17,18,19,20,21};

main(String[] args) {
  copyColumnsToHand(1);
  printHand(); // Not part of the project, but simple to implement
  copyColumnsToHand(2);
  printHand();
  copyColumnsToHand(3);
  printHand();
}

Then make sure your hand contains the correct sequence depending which is the column that you input. Maybe you can implement a function that prints the hand array for debugging purposes.

If you do that, then this should by your output:

15 16 17 18 19 20 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 <- Collected columns 3, 1, 2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 <- Collected columns 1, 2, 3
8 9 10 11 12 13 14 15 16 17 18 19 20 21 1 2 3 4 5 6 7 <- Collected columns 2, 3, 1

Implementation suggestion 2

Maybe creating a triplet of functions to collect each column can help? Maybe a function that collects column 1 and places the cards in the hand? Maybe such function should have an argument that indicates in which index of the hand the program should start putting cards in? Just maybe? :)

Like:

Hey function, collect column 1 and place the cards in the hand starting in position 7…

Function:

Ok, here you go:

? ? ? ? ? ? ? 1 2 3 4 5 6 7 ? ? ? ? ? ? ?

(Question marks mean we don’t know what it is there, because we didn’t place stuff there yet :)

Finishing the game!

Hint: At this point every part of the project should be working. But as you bring things together they may interact the wrong way. If that happens and parts work but the whole doesn’t, don’t despair! Start commenting out your code and adding a piece at a time. This will help figuring out where the problem is. Then it’s a matter of fixing it.

As usual, if you get stuck, ask for help!

Demo

Once you have finished, show the lab instructor what you did in Lab 6.

Beyond the lab

Now, until the deadline, make sure everything is working and submit it following the instructions in the project 2 description.

Extra credit

You want more, you say? Well, what about this for extra 10%? Implement card shuffling. Let’s confuse the player a bit more :) after all this is supposed to be magic!

An algorithm to shuffle the cards is the Fisher-Yates shuffle algorithm.

This is how it works:

1. Have an array with all the elements filled in.
2. For i = length-1 down to 1 (inclusive)
   • Pick a random number r ranging between 0 and i.
   • Swap the i-th element of the array with the r-th element of the array.
   • Continue loop.
3. The array elements are now in a random order.

Example:

Implement this algorithm and shuffle the cards in the magician’s hand before starting the game.

If there is something else you want to try for extra credit, let me know and I’ll let you know if that’s acceptable.