all tasks

Task/Sorting-algorithms-Quicksort/VBA/sorting-algorithms-quicksort.vba

@@ -0,0 +1,63 @@
+Public Sub Quick(a() As Variant, last As Integer)
+' quicksort a Variant array (1-based, numbers or strings)
+Dim aLess() As Variant
+Dim aEq() As Variant
+Dim aGreater() As Variant
+Dim pivot As Variant
+Dim naLess As Integer
+Dim naEq As Integer
+Dim naGreater As Integer
+
+If last > 1 Then
+    'choose pivot in the middle of the array
+    pivot = a(Int((last + 1) / 2))
+    'construct arrays
+    naLess = 0
+    naEq = 0
+    naGreater = 0
+    For Each el In a()
+      If el > pivot Then
+        naGreater = naGreater + 1
+        ReDim Preserve aGreater(1 To naGreater)
+        aGreater(naGreater) = el
+      ElseIf el < pivot Then
+        naLess = naLess + 1
+        ReDim Preserve aLess(1 To naLess)
+        aLess(naLess) = el
+      Else
+        naEq = naEq + 1
+        ReDim Preserve aEq(1 To naEq)
+        aEq(naEq) = el
+      End If
+    Next
+    'sort arrays "less" and "greater"
+    Quick aLess(), naLess
+    Quick aGreater(), naGreater
+    'concatenate
+    P = 1
+    For i = 1 To naLess
+      a(P) = aLess(i): P = P + 1
+    Next
+    For i = 1 To naEq
+      a(P) = aEq(i): P = P + 1
+    Next
+    For i = 1 To naGreater
+      a(P) = aGreater(i): P = P + 1
+    Next
+End If
+End Sub
+
+Public Sub QuicksortTest()
+Dim a(1 To 26) As Variant
+
+ 'populate a with numbers in descending order, then sort
+ For i = 1 To 26: a(i) = 26 - i: Next
+ Quick a(), 26
+ For i = 1 To 26: Debug.Print a(i);: Next
+ Debug.Print
+ 'now populate a with strings in descending order, then sort
+ For i = 1 To 26: a(i) = Chr$(Asc("z") + 1 - i) & "-stuff": Next
+ Quick a(), 26
+ For i = 1 To 26: Debug.Print a(i); " ";: Next
+ Debug.Print
+End Sub