Unique Number Arrays?

[Programmer_Jpk]

i was wondering how people go about getting Unique Number Arrays? cause a lot of people do it very differently , seen people with 100 lines of code, others with 10.. my way lately has been using HashTables

        Dim a As Integer  Just a Counting Value
        Dim RNS As Integer = 100  Random Numbers im just using 100, cause i can
        Dim RandomValues As New Hashtable  Hash Table, Of Course o.o
        Dim RandValue As Integer  Random Number
        While a <> RNS
            Randomize()
            RandValue = Int((RNS - 0 + 1) * Rnd()) + 0  highest - Lowest + 1 ect.. 
            While RandomValues.ContainsValue(RandValue)  If Hastable Contains The Value, Go nuts till it gets it
                RandValue = Int((RNS - 0 + 1) * Rnd()) + 0
            End While
            RandomValues(a) = RandValue if it got it, set it..
            a += 1  Repeat
        End While

So Yeah o.o, just wondering how people go about their random values.. and weather or not there is more simpler stuff i could steal :]

 

[PlausiblyDamp]

Are you looking at having the numbers 1 through 100 put into a random order or just 100 random numbers that could be larger than 100?

 

[Programmer_Jpk]

This code produces 100 values, checks if its already entered into the hashtable then adds it if it isnt

Example: Say you want 52 card values shuffled for a card game you would change the 100 to 52, and 0 to 1

        Dim a As Integer 
        Dim HighVal As Integer = 52  Highest Value Wanted
        Dim LowVal as integer = 1  Lowest Value Wanted

        Dim RandomValues As New Hashtable
        Dim RandValue As Integer

        While a <> HighVal 
            Randomize()
            RandValue = Int((HighVal- LowVal + 1) * Rnd()) + LowVal
            While RandomValues.ContainsValue(RandValue) 
                RandValue = Int((HighVal- 0 + 1) * Rnd()) + 0
            End While
            RandomValues(a) = RandValue
            a += 1
        End While

And this would add 52 Values into the Hashtable, all random

If you want just add a text box and
TextBox1.Text = TextBox1.Text & RandValue & ", "
after the a += 1
And you would be able to test it out for yourself

Which This Time Produced
"38, 34, 22, 43, 33, 24, 27, 30, 18, 4, 31, 2, 14, 28, 10, 49, 17, 8, 29, 23, 41, 20, 3, 9, 5, 0, 35, 1, 15, 25, 19, 52, 26, 47, 44, 42, 45, 46, 37, 12, 39, 32, 36, 7, 40, 48, 16, 11, 21, 51, 6, 13"

All i want to know is how everyone else goes about getting their own random numbers, cause most people do it differently to a degree

 

[MrPaul]

Pick two and swap!

So Yeah o.o, just wondering how people go about their random values.. and weather or not there is more simpler stuff i could steal :]

There certainly is a simpler way of achieving this. If your intent is to create a list containing all numbers from LowVal to HighVal, in a random order, the simplest solution is to add them all to the list sequentially, and then jumble them up by repeatedly swapping two randomly chosen items. This is easiest/fastest with an array.

The reason this is preferable, is that your implementation will take an indeterminate amount of time to execute. The more items that get added to the list, the more "collisions" will occur - to the point that for the last value, the loop has to keep generating random numbers until the one possible valid number is randomly chosen. For large values of HighVal, this could take forever! Compare this to the "swap items randomly" method, which will have a predictable number of swaps, and therefore a predictable time function.

Good luck!

 

[snarfblam]

Re: Pick two and swap!

Another method that guaruntees a random order would be to fill an array by picking random insertion points. Using the 52 example, start by initializing an array with 52 dummy values that indicate that that spot is empty (-1 would be typical, in this case 0 will also work).

You start with value 1, and pick a random number from 0 to 51 for the insertion, and place the 1 at that index. Next time, pick a random number from 0 to 50, and count through that many empty spaces (i.e. count through empty spaces, skipping used spots), then put the 2 at the nth empty spot. Then pick a random number from 0 to 49 in put the 3 in that empty spot. Using random numbers with a range equal to the number of empty spots remaining gives all empty spots an equal chance of being used each iteration.

Of course, if you are making a card game, you may want to use a more "legitimate" shuffling algorithm to make the game more "authentic".

 

[PlausiblyDamp]

Re: Pick two and swap!

If the data is in an array you could also use Array.Sort with a bunch of random numbers as the key

int[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
Random r = new Random();
byte[] b = new byte[numbers.Count()];
r.NextBytes(b);
Array.Sort(b, numbers);

although for large array numbers using a byte as a random key might not be random enough.