shuffle string of array

[sanjibnanda]

Hi ,

How can i shuffle string of array

alphabets = {"A", "B", "C", "D", "E", "F", "G", "H", "I", "J"};

TO SOME RANDOM STATE LIKE

alphabets = {"C", "A", "I", "D", "G", "J", "H", "H", "B", "F"};

 

[MLDev]

' Knuth's Algorithm P
Dim n As Int = alphabets.Length
Dim r As Int
Dim t As String
   
For i = 0 To n - 1
   r = Rnd(i, n)
   t = alphabets(i)
   alphabets(i) = alphabets(r)
   alphabets(r) = t
Next

 

[sanjibnanda]

shuffle Array As string

' Knuth's Algorithm P
Dim n As Int = alphabets.Length
Dim r As Int
Dim t As String
   
For i = 0 To n - 1
   r = Rnd(i, n)
   t = alphabets(i)
   alphabets(i) = alphabets(r)
   alphabets(r) = t
Next

Thanks for hint MLdev ... i converted it to sub , may be helpful for some Newbie

Sub ShuffleArray(arr() As String)
   Dim n As Int = arr.Length-1
Dim r As Int
Dim t As String
    
For i = 0 To n - 1
    r = Rnd(i, n)
    t = arr(i)
    arr(i) = arr(r)
    arr(r) = t
Next
Return arr
End Sub

How to use

ShuffleArray(YourArr)

B4A forum is wonderful as long as people like you live there...

it worked like a charm...thanks again to you and Knuth's Algorithm P
regards
sanjib

 

[MLDev]

With this line in your sub:

Dim n As Int = arr.Length-1

The last element in the array will always be the same. It should be:

Dim n As Int = arr.Length

EDIT

And this line in my code:

For i = 0 To n - 1

should be:

For i = 0 To n - 2

:signOops:

 

[sanjibnanda]

Acknowledged with regards

 

[DrownedBat]

Any way to reverse this process?

take alphabets = {"C", "A", "I", "D", "G", "J", "H", "H", "B", "F"};
and arrange it back into alphabets = {"A", "B", "C", "D", "E", "F", "G", "H", "I", "J"};

 

[sorex]

I guess the easiest would be to loop through the elements and put them into a list, sort the list, write it back to the array.

or you can write your own sort routine on the array.

 

[James Chamblin]

Any way to reverse this process?

take alphabets = {"C", "A", "I", "D", "G", "J", "H", "H", "B", "F"};
and arrange it back into alphabets = {"A", "B", "C", "D", "E", "F", "G", "H", "I", "J"};

Check out this thread https://www.b4x.com/android/forum/threads/sorting-algorithms-teaching-with-basic4android.8548/

 

[Erel]

Use a list instead of an array and call List.Sort to sort the items.