Randomise a list of objects

Blitz3D Forums/Blitz3D Programming/Randomise a list of objects

Neo Genesis10

(Posted 2010) [#1]

I have a list of objects in an array I want to randomise. I'm looking for the most efficient way of doing this. Current methods involve systematically stepping through the array and, with a random number generatator, picking two points of the array to 'swap' with each other.

Theres got to be a faster method though, so if anyone has any ideas I'd appreciate them.

Jiffy

(Posted 2010) [#2]

You have an array of 10 elements
Make a rnd number 1-10 (returns 7)
index that (7th) element as 1st
remove from list
You now have an array of 9 elements.
do the same to get the 2nd.
and so on.
just one technique.

Kryzon

(Posted 2010) [#3]

I wrote a function for this long ago, you can use it if you want:

;You need the array you want the elements to be randomly arranged, and the max number of elements that array should have:

Const MaxSlots = 10
Dim Array(MaxSlots-1)


Function RandomlyArrangeArray()

       Local Temp[MaxSlots-1] 
       Local TempSlots = MaxSlots-1
       Local Random

       For I = 0 To MaxSlots-1
              Temp[I] = I      ;This loop populates the temporary array. You should change this to fit your needs.
       Next

       For I = 0 To MaxSlots-1
	
              Random = Rand(0,TempSlots)
              Array(I) = Temp[Random]      ;Note that you need to specify which array to re-arrange.
	
              For I2 = 0 To MaxSlots-1 

                     If (I2 < TempSlots) Then 
		    
                            If (I2 >= Random) Then Temp[I2] = Temp[I2+1]
          
                     EndIf 
	
              Next	 
	
              TempSlots = TempSlots - 1     
       Next 

End Function

PRO's: Uses a local array and variables, so it's very light.

CON's: You need to write the name of the array you want to re-arrange, inside the function.

Don't mind the function's big name.