Initial data commit

Task/Sorting-algorithms-Merge-sort/FreeBASIC/sorting-algorithms-merge-sort.basic

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+' FB 1.05.0 Win64
+
+Sub copyArray(a() As Integer, iBegin As Integer, iEnd As Integer, b() As Integer)
+  Redim b(iBegin To iEnd - 1) As Integer
+  For k As Integer = iBegin To iEnd - 1
+    b(k) = a(k)
+  Next
+End Sub
+
+' Left source half is  a(iBegin  To iMiddle-1).
+' Right source half is a(iMiddle To iEnd-1).
+' Result is            b(iBegin  To iEnd-1).
+Sub topDownMerge(a() As Integer, iBegin As Integer, iMiddle As Integer, iEnd As Integer, b() As Integer)
+  Dim i As Integer = iBegin
+  Dim j As Integer = iMiddle
+
+  ' While there are elements in the left or right runs...
+  For k As Integer = iBegin To iEnd - 1
+  ' If left run head exists and is <= existing right run head.
+    If i < iMiddle AndAlso (j >= iEnd OrElse a(i) <= a(j)) Then
+      b(k) = a(i)
+      i += 1
+    Else
+      b(k) = a(j)
+      j += 1
+    End If
+  Next
+End Sub
+
+' Sort the given run of array a() using array b() as a source.
+' iBegin is inclusive; iEnd is exclusive (a(iEnd) is not in the set).
+Sub topDownSplitMerge(b() As Integer, iBegin As Integer, iEnd As Integer, a() As Integer)
+  If (iEnd - iBegin) < 2 Then Return  '' If run size = 1, consider it sorted
+  ' split the run longer than 1 item into halves
+  Dim iMiddle As Integer = (iEnd + iBegin) \ 2  '' iMiddle = mid point
+  ' recursively sort both runs from array a() into b()
+  topDownSplitMerge(a(), iBegin,  iMiddle, b())  '' sort the left  run
+  topDownSplitMerge(a(), iMiddle, iEnd, b())     '' sort the right run
+  ' merge the resulting runs from array b() into a()
+  topDownMerge(b(), iBegin, iMiddle, iEnd, a())
+End Sub
+
+' Array a() has the items to sort; array b() is a work array (empty initially).
+Sub topDownMergeSort(a() As Integer, b() As Integer, n As Integer)
+  copyArray(a(), 0, n, b())  '' duplicate array a() into b()
+  topDownSplitMerge(b(), 0, n, a())  '' sort data from b() into a()
+End Sub
+
+Sub printArray(a() As Integer)
+  For i As Integer = LBound(a) To UBound(a)
+    Print Using "####"; a(i);
+  Next
+  Print
+End Sub
+
+Dim a(0 To 9) As Integer = {4, 65, 2, -31, 0, 99, 2, 83, 782, 1}
+
+Dim b() As Integer
+Print "Unsorted : ";
+printArray(a())
+topDownMergeSort a(), b(), 10
+Print "Sorted   : ";
+printArray(a())
+Print
+Dim a2(0 To 8) As Integer = {7, 5, 2, 6, 1, 4, 2, 6, 3}
+Erase b
+Print "Unsorted : ";
+printArray(a2())
+topDownMergeSort a2(), b(), 9
+Print "Sorted   : ";
+printArray(a2())
+Print
+Print "Press any key to quit"
+Sleep