Permutations: Difference between revisions

=={{header|VBA}}==

Based on the Pascal version above.

<lang VBA>

Public Sub Permute(n As Integer, Optional printem As Boolean = True)

'generate, count and print (if printem is not false) all permutations of first n integers

Dim P() As Integer

Dim count As Long

dim Last as boolean

Dim t, i, j, k As Integer

If n <= 1 Then

Debug.Print "give a number greater than 1!"

Exit Sub

End If

'initialize

ReDim P(n)

For i = 1 To n: P(i) = i: Next

count = 0

Last = False

Do While Not Last

'print?

If printem Then

For t = 1 To n: Debug.Print P(t);: Next

Debug.Print

End If

count = count + 1

Last = True

i = n - 1

Do While i > 0

If P(i) < P(i + 1) Then

Last = False

Exit Do

End If

i = i - 1

Loop

If Not Last Then

j = i + 1

k = n

While j < k

' swap p(j) and p(k)

t = P(j)

P(j) = P(k)

P(k) = t

j = j + 1

k = k - 1

Wend

j = n

While P(j) > P(i)

j = j - 1

Wend

j = j + 1

'swap p(i) and p(j)

t = P(i)

P(i) = P(j)

P(j) = t

End If 'not last

Loop 'while not last

Debug.Print "Number of permutations: "; count

End Sub

</lang>

Sample dialogue:

<pre>

permute 1

give a number greater than 1!

permute 2

1 2

2 1

Number of permutations: 2

permute 4

1 2 3 4

1 2 4 3

1 3 2 4

1 3 4 2

1 4 2 3

1 4 3 2

2 1 3 4

2 1 4 3

2 3 1 4

2 3 4 1

2 4 1 3

2 4 3 1

3 1 2 4

3 1 4 2

3 2 1 4

3 2 4 1

3 4 1 2

3 4 2 1

4 1 2 3

4 1 3 2

4 2 1 3

4 2 3 1

4 3 1 2

4 3 2 1

Number of permutations: 24

permute 10,False

Number of permutations: 3628800

</pre>