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{ ******************************************************************
Quick sort
****************************************************************** }
unit uqsort;
interface
uses
utypes;
procedure QSort(X : PVector; Lb, Ub : Integer);
{ ------------------------------------------------------------------
Sorts the elements of vector X in increasing order (quick sort)
------------------------------------------------------------------ }
procedure DQSort(X : PVector; Lb, Ub : Integer);
{ ------------------------------------------------------------------
Sorts the elements of vector X in decreasing order (quick sort)
------------------------------------------------------------------ }
implementation
procedure QSort(X : PVector; Lb, Ub : Integer);
{ Quick sort in ascending order - Adapted from Borland's BP7 demo }
procedure Sort(L, R : Integer);
var
I, J : Integer;
U, V : Float;
begin
I := L;
J := R;
U := X^[(L + R) div 2];
repeat
while X^[I] < U do I := I + 1;
while U < X^[J] do J := J - 1;
if I <= J then
begin
V := X^[I]; X^[I] := X^[J]; X^[J] := V;
I := I + 1; J := J - 1;
end;
until I > J;
if L < J then Sort(L, J);
if I < R then Sort(I, R);
end;
begin
Sort(Lb, Ub);
end;
procedure DQSort(X : PVector; Lb, Ub : Integer);
{ Quick sort in descending order - Adapted from Borland's BP7 demo }
procedure Sort(L, R : Integer);
var
I, J : Integer;
U, V : Float;
begin
I := L;
J := R;
U := X^[(L + R) div 2];
repeat
while X^[I] > U do I := I + 1;
while U > X^[J] do J := J - 1;
if I <= J then
begin
V := X^[I]; X^[I] := X^[J]; X^[J] := V;
I := I + 1; J := J - 1;
end;
until I > J;
if L < J then Sort(L, J);
if I < R then Sort(I, R);
end;
begin
Sort(Lb, Ub);
end;
end.
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