Programming Challenges?

[Fobic]

Before we move on too far here's my attempts at the previous challenges
Both are VB.net console Apps.

Mutliples of 3 and 5 without using any type of Modulus functions:

Spoiler: 

Module MultiplesOf3And5
 
   Sub Main()
      Dim aList As New SortedList
 
      '//iterate through all the possible multiples
      '//and store any previously unfound ones in a Sorted List
      For intFifteens As Integer = 3 * 5 To 100 Step 3 * 5
         aList.Add(intFifteens, " is a multiple of both 3 and 5")
      Next intFifteens
 
      For intFives As Integer = 5 To 100 Step 5
         If Not aList.Contains(intFives) Then aList.Add(intFives, " is a multiple of 5")
      Next intFives
 
      For intThrees As Integer = 3 To 100 Step 3
         If Not aList.Contains(intThrees) Then aList.Add(intThrees, " is a multiple of 3")
      Next intThrees
 
      '//Display the contents of the Sorted List
      For intIndex As Integer = 0 To aList.Count - 1
         Console.WriteLine(aList.GetKey(intIndex) & aList.GetByIndex(intIndex))
      Next intIndex
      Console.ReadKey(True)
 
   End Sub
 
End Module

The For/Next Loops step through each multiple
of 3*5, 5 and 3 and adds the multiples to a Sorted List
if they haven't already been added.

A Sorted List is a list where each item in the list
consists of two parts: a Key part and a Value part.
The list is automatically sorted on the Key part.

We store each iterated multiple in the the Key part
and text explaining the type of multiple is
stored in the corresponding Value part.

Then we just display the contents of the Sorted List.

And a quick and dirty way of calculating the Monty Hall probabilities
(with thanks to Damien for coding tips)

Spoiler: 

Module MontyHall
 
   Sub Main()
      Dim aRnd As New Random
      Dim Doors() As String = {"Goat", "Goat", "Goat"}   '//put 3 Goats behind 3 doors
 
      Dim intDoorWithCar As Integer                '//Number of the Door with the Car
      Dim intDoorChosen As Integer                 '//Number of the Door we choose
      Dim intChosenDoorWinCount As Integer = 0     '//Accumulated wins sticking with original chosen door
      Dim intAlternateDoorWinCount As Integer = 0  '//Accumulated wins swapping to alternate door
      Dim intNumIterations As Integer = 100000
 
      For intI As Integer = 1 To intNumIterations
         intDoorWithCar = aRnd.Next(3)    '//Randomly replace one of the 
         Doors(intDoorWithCar) = "Car"    '//   3 Goats with a Car
 
         intDoorChosen = aRnd.Next(3)     '//Choose one of the 3 doors at random
         If intDoorChosen = intDoorWithCar Then intChosenDoorWinCount += 1 Else intAlternateDoorWinCount += 1
 
         Doors(intDoorWithCar) = "Goat"   '//Replace the Car with a Goat
      Next intI                           '// and go around again
 
      Console.WriteLine("Percentage probability of winning Car:")
      Console.WriteLine("Keeping Original Choice of Door   = " & Format(intChosenDoorWinCount / intNumIterations, "Percent"))
      Console.WriteLine("Swapping Choice to the Other Door = " & Format(intAlternateDoorWinCount / intNumIterations, "Percent"))
      Console.ReadKey(True)
 
   End Sub
 
End Module

We choose one of the 3 doors at random.
Monty removes one of the remaining 2 doors
that has a goat behind it.
We don't need to know which door, just that a goat
has been removed and now we only have 2 doors left
- A goat behind one and a Car behind the other, and
that our chosen door is one of them.

The If/THEN/ELSE line of the code works as follows:

If we stick with our choice and win, then
increase the count of wins for the Chosen Door.
(in the "Swapping Doors Scenario" we would have lost)

If we stick with our choice and lose, then in the
"Swapping Doors Scenario" we would have won, so
increase the count of wins for the Alternate Door.

[punky]

Originally Posted by Damien

Nice Punky. It's only not 'proper' OO because it's limited in scope (i.e the project is too small) to use many features. OO becomes more central to your application structure in bigger applications anyway. I mean all you can do is make door an object really...(which you did, smart).

You probably know this but when accessing a variable outside of it's containing class you should make it a property..

Indeedy. Normally I make all class variables private with the proper accessors (proper encapsulation) but I didn't just because it meant typing lines and lines of code for no real benefits. I would for any "production"-level app.

Here's the Door class with proper encapsulation (I would normally prefix private class variables with _ (like _doorNumber) but that's just convention)

Spoiler: 

    //class to represent the door
    class Door
    {
        private int doorNumber;
        private Boolean open = false;
        private String prize;

        //constructor, this happens when a door is created
        public Door(int doorNumber, String prize)
        {
            this.doorNumber = doorNumber;
            this.prize = prize;
        }

        //this is called when we Console.WriteLine a door. We have to override the default ToString() method
        public override String ToString()
        {
            String status = open ? "Open" : "Closed";
            return "Door " + doorNumber + ": " + prize + " (" + status + ")";
        }

        public bool Open
        {
            get 
            {
                return open;
            }
            set
            {
                open = value;
            }
        }

        public String Prize
        {
            get
            {
                return prize;
            }
            set
            {
                prize = value;
            }

        }

        public int DoorNumber
        {
            get
            {
                return doorNumber;
            }
            set
            {
                doorNumber = value;
            }
        }
    }

I tend to find because I use OO a lot now that unless something is really small (i.e. an algorithm rather than a game) that I start building it in OO first and then scaling back if it really gets unnecessary.

BTW the point being of all that is that you can control what comes in and out of the class. For example for the prize, I can make sure its one of x pre-determined prizes, that a door number is greater than 0, etc.

Originally Posted by punky

I tend to find because I use OO a lot now that unless something is really small (i.e. an algorithm rather than a game) that I start building it in OO first and then scaling back if it really gets unnecessary.

BTW the point being of all that is that you can control what comes in and out of the class. For example for the prize, I can make sure its one of x pre-determined prizes, that a door number is greater than 0, etc.

Yes, Well all app in C# eventually needs to be done via OO. It's all I really work in (other than these apps).

[punky]

Here's my mortgage length calculator:

Spoiler: 

I'm sure there's a way to do it without a loop, but can't think of it atm.

Assuming £100,000 with a 4.75% rate and paying off £700/month

            float mortgage = 100000f;
            float rate = 4.75f; //%
            int repaymentAmount = 700;

            float months = 0;

            while (mortgage > 0)
            {
                mortgage *= (1 + ((rate / 12) / 100));
                mortgage -= repaymentAmount;
                months++;
            }

            Console.WriteLine("Repayment duration: " + months + " months - " + (int)(months/12) + " Years and " + (months%12) + " months.");

Result:

Repayment duration: 211 months - 17 Years and 7 months.

[danielf]

Here's my mortgage calculator, using recursion

Spoiler: 

(defun mortgage (balance payment rate months)
(if
(< balance 0)
(print months)
(mortgage (- (+ (* (/ rate 12) balance) balance) payment) payment rate (+ months 1))))

How do you get indentation in the code? My code is indented when I paste it, but I lose indentation in the spoiler tags. Even spaces don't stick...

[punky]

I did wonder about recursion...

Spoiler: 

class Program
    {
        static int months = 0;

        static void Main(string[] args)
        {
            CalculateMortgage(100000f, 4.75f, 700);
            Console.ReadLine();
        }

        static void CalculateMortgage(float mortgage,float rate,int repaymentAmount)
        {

            if (mortgage > 0)
            {
                months++;
                CalculateMortgage((mortgage * (1 + ((rate / 12) / 100)) - repaymentAmount), rate, repaymentAmount);
                
            }
            else
            {
                Console.WriteLine("Repayment duration: " + months + " months - " + (int)(months / 12) + " Years and " + (months % 12) + " months.");
            }

        }
    }

Result:

Repayment duration: 211 months - 17 Years and 7 months.

I'm still sure there must be an equation for it rather than just iterating through.

[danielf]

Originally Posted by punky

I'm still sure there must be an equation for it rather than just iterating through.

Probably, but it is a programming challenge, not a Maths challenge

[Fobic]

Originally Posted by danielf

How do you get indentation in the code? My code is indented when I paste it, but I lose indentation in the spoiler tags. Even spaces don't stick...

Try wrapping the code in [Code][/Code] tags inside the [Spoiler][/Spoiler] tags.

i.e.

[Spoiler][Code]
.....
......
[/Code][/Spoiler]

or similar.


Can anyone tell me how to stop my code appearing in colour when I Copy from the standard VB 2005 Express Editor and Paste in here ??

like this:

PrivateSub StopTheseColours()
Dim aString AsString = "123"
'How to paste this code in Black and White?
EndSub

[Druchii]

Paste into Notepad first?
Or, highlight the pasted text and set the font color to black?

I did it simply but the results where wrong. I thought interest was a set % amount of the total balance. I take it you need to apply it per month instead?

[Druchii]

Originally Posted by Damien

I did it simply but the results where wrong. I thought interest was a set % amount of the total balance. I take it you need to apply it per month instead?

From what i can work out, some apply the interest yearly, others monthly. It all depends.

Mine calculates on the yearly balance, however.

[punky]

Originally Posted by Damien

I did it simply but the results where wrong. I thought interest was a set % amount of the total balance. I take it you need to apply it per month instead?

Yup. Because the longer you take to repay the mortgage, the more interest you pay.

[danielf]

Originally Posted by Fobic

Try wrapping the code in [Code][/Code] tags inside the [Spoiler][/Spoiler] tags.

i.e.

[Spoiler][Code]
.....
......
[/Code][/Spoiler]

or similar.

Cheers!

Spoiler: 

(defun mortgage (balance payment rate months)
  (if
      (< balance 0)
      (print months)
    (mortgage (- (+ (* (/ rate 12) balance) balance) payment) payment rate (+ months 1))))

[Fobic]

Originally Posted by Druchii

Paste into Notepad first?
Or, highlight the pasted text and set the font color to black?

Thanks for answering .
I'd already used the Paste to Notepad route which works but unfortunately strips out blank lines between code lines, which means you have to edit the code in Notepad to double every blank line.

Changing the Font colour is a nice thought, but the coloured code in here is also broken code. Spaces between keywords are stripped and the indentation is also stripped.

Guess I'm just looking for the laziest way of doing it (as usual, lol).

[punky]

Originally Posted by Fobic

Thanks for answering .
I'd already used the Paste to Notepad route which works but unfortunately strips out blank lines between code lines, which means you have to edit the code in Notepad to double every blank line.

Changing the Font colour is a nice thought, but the coloured code in here is also broken code. Spaces between keywords are stripped and the indentation is also stripped.

Guess I'm just looking for the laziest way of doing it (as usual, lol).

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