Binaryworld - SelectionSort - Short, simple and sloooow ... [ VB -> Datastructure ]

' SelectionSort. Short, simple and sloooow. This is another O(N^2) sort that
' should never be used on long lists. Like InsertionSort,
' it needs no extra memory (in place) and preserves the existing order of
' records with equal keys. Unfortunately, it's slower,
' and there's no reason to use it instead of InsertionSort. Works by looking
' thru the list for the smallest key and placing it first,
' then looking for the next largest, and so on. If the slow linear search for
' each key is replaced by a faster "priority queue" approach,
' a reasonably fast algorithm can be created (see HeapSort). Two versions are
' given. pSelSortS is an indirect (pointerized) version for strings,
' which can be adapted to doubles by changing the declaration of A().
' SelSortL is a direct version for longs, which can be adapted to integers.
'
' Speed: Don't ask.
'
' Bottom line: Included because it's a clear and simple approach,
' but too slow to be useful.

' Usage:

Dim S1(L To R) As String
Dim P1(L To R) As Long
Dim L1(L To R) As Long

For I = L To R
  S1(I) = GetRandomString()
  P1(I) = I
  L1(I) = GetRandomLong()
Next I

pSelSortS L, R, S1, P1
SelSortL L, R, L1

' CODE:

Sub pSelSortS(L As Long, R As Long, A() As String, P() As Long)
  Dim I As Long
  Dim J As Long
  Dim Min As Long
  Dim TMP As Long

  For I = L To R - 2
  'Start with the first key.
    Min = I
  'Compare to each key to the right
    For J = I + 1 To R
    'Every time we find a lower value, keep that pointer.
      If A(P(J)) < A(P(Min)) Then
        Min = J
      End If
    Next J
  'When we've scanned all keys, swap the low key's pointer to the end of the
  ' sorted list.
    TMP = P(I)
    P(I) = P(Min)
    P(Min) = TMP
  Next I
End Sub

Sub SelSortL(L As Long, R As Long, A() As Long)
  Dim I As Long
  Dim J As Long
  Dim Min As Long
  Dim TMP As Long

  For I = L To R - 2
    Min = I
    For J = I + 1 To R
      If A(J) < A(Min) Then
        Min = J
      End If
    Next J
    TMP = A(I)
    A(I) = A(Min)
    A(Min) = TMP
  Next I
End Sub