- 4.67.2.64. -
Table of Contents
4. Standard Units
4.67. System - Built-in routines
4.67.2. System Unit Procedures and Functions
4.67.2.64. QSort procedure
4.67.2.64. QSort procedure
Targets: MS-DOS, OS/2, Win32
System Unit
QSort procedure performs a quick sort.
Declaration:
procedure QSort(base: Pointer; num, width: Integer;
function CompFunc conv arg_based
(const elem1, elem2: Pointer): Boolean);
Remarks:
The QSort procedure implements a quick-sort algorithm to sort an array
of num elements, each of width bytes. The argument base is
a pointer to the base of the array to be sorted. QSort replaces this
array with the sorted elements. The argument CompFunc is a user-supplied
function that compares two array elements and returns a value specifying their
relationship. QSort calls the CompFunc function one or more times
during the sort, passing pointers to two array elements on each call. The
routine must compare the elements, then return one of the following values:
| Return Value | Description |
|---|
| < 0 | elem1 less than elem2 |
| 0 | elem1 equivalent to elem2 |
| > 0 | elem1 greater than elem2 |
Example:
// This program uses qsort to sort
// an array of Integers in ascending order.
{$ifdef __GUI__}
uses WinCRT;
{$endif}
function CompFunc conv arg_based
(const elem1, elem2: Pointer): Boolean;
begin
Result := Integer(elem1^) > Integer(elem2^);
end;
procedure PrintArray(hdr: String; arg: array(1) of Integer);
var
i: Integer;
begin
Write(hdr);
for i := 0 to high(arg)[0] do
Write(arg[i], ' ');
Writeln;
end;
var
a: array [0..9] of Integer;
i: Integer;
begin
for i := 0 to 9 do
a[i] := Random(100) - Random(100);
PrintArray('Initial: ', a);
QSort(@a, 10, SizeOf(Integer), CompFunc);
PrintArray(' Sorted: ', a);
end.
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