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{
> Can you show me any version of thew quick sort that you may have? I've
> never seen it and never used it before. I always used an insertion sort
> For anything that I was doing.
Here is one (long) non-recursive version, quite fast.
}
Type
_Compare = Function(Var A, B) : Boolean;{ QuickSort Calls This }
{ --------------------------------------------------------------- }
{ QuickSort Algorithm by C.A.R. Hoare. Non-Recursive adaptation }
{ from "ALGORITHMS + DATA STRUCTURES = ProgramS" by Niklaus Wirth }
{ Prentice-Hall, 1976. Generalized For unTyped arguments. }
{ --------------------------------------------------------------- }
Procedure QuickSort(V : Pointer; { To Array of Records }
Cnt : Word; { Record Count }
Len : Word; { Record Length }
ALessB : _Compare); { Compare Function }
Type
SortRec = Record
Lt, Rt : Integer
end;
SortStak = Array [0..1] of SortRec;
Var
StkT,
StkM,
Ki, Kj,
M : Word;
Rt, Lt,
I, J : Integer;
Ps : ^SortStak;
Pw, Px : Pointer;
Procedure Push(Left, Right : Integer);
begin
Ps^[StkT].Lt := Left;
Ps^[StkT].Rt := Right;
Inc(StkT);
end;
Procedure Pop(Var Left, Right : Integer);
begin
Dec(StkT);
Left := Ps^[StkT].Lt;
Right := Ps^[StkT].Rt;
end;
begin {QSort}
if (Cnt > 1) and (V <> Nil) Then
begin
StkT := Cnt - 1; { Record Count - 1 }
Lt := 1; { Safety Valve }
{ We need a stack of Log2(n-1) entries plus 1 spare For safety }
Repeat
StkT := StkT SHR 1;
Inc(Lt);
Until StkT = 0; { 1+Log2(n-1) }
StkM := Lt * SizeOf(SortRec) + Len + Len; { Stack Size + 2 Records }
GetMem(Ps, StkM); { Allocate Memory }
if Ps = Nil Then
RunError(215); { Catastrophic Error }
Pw := @Ps^[Lt]; { Swap Area Pointer }
Px := Ptr(Seg(Pw^), Ofs(Pw^) + Len); { Hold Area Pointer }
Lt := 0;
Rt := Cnt - 1; { Initial Partition }
Push(Lt, Rt); { Push Entire Table }
While StkT > 0 Do
begin { QuickSort Main Loop }
Pop(Lt, Rt); { Get Next Partition }
Repeat
I := Lt; J := Rt; { Set Work Pointers }
{ Save Record at Partition Mid-Point in Hold Area }
M := (LongInt(Lt) + Rt) div 2;
Move(Ptr(Seg(V^), Ofs(V^) + M * Len)^, Px^, Len);
{ Get Useful Offsets to speed loops }
Ki := I * Len + Ofs(V^);
Kj := J * Len + Ofs(V^);
Repeat
{ Find Left-Most Entry >= Mid-Point Entry }
While ALessB(Ptr(Seg(V^), Ki)^, Px^) Do
begin
Inc(Ki, Len);
Inc(I)
end;
{ Find Right-Most Entry <= Mid-Point Entry }
While ALessB(Px^, Ptr(Seg(V^), Kj)^) Do
begin
Dec(Kj, Len);
Dec(J)
end;
{ if I > J, the partition has been exhausted }
if I <= J Then
begin
if I < J Then { we have two Records to exchange }
begin
Move(Ptr(Seg(V^), Ki)^, Pw^, Len);
Move(Ptr(Seg(V^), Kj)^, Ptr(Seg(V^), Ki)^, Len);
Move(Pw^, Ptr(Seg(V^), Kj)^, Len);
end;
Inc(I);
Dec(J);
Inc(Ki, Len);
Dec(Kj, Len);
end; { if I <= J }
Until I > J; { Until All Swaps Done }
{ We now have two partitions. At left are all Records }
{ < X, and at right are all Records > X. The larger }
{ partition is stacked and we re-partition the residue }
{ Until time to pop a deferred partition. }
if (J - Lt) < (Rt - I) Then { Right-Most Partition is Larger }
begin
if I < Rt Then
Push(I, Rt); { Stack Right Side }
Rt := J; { Resume With Left }
end
else { Left-Most Partition is Larger }
begin
if Lt < J Then
Push(Lt, J); { Stack Left Side }
Lt := I; { Resume With Right }
end;
Until Lt >= Rt; { QuickSort is now Complete }
end;
FreeMem(Ps, StkM); { Free Stack and Work Areas }
end;
end; {QSort}
{ --------------------------- CUT ----------------------------}
{
ALEXANDER CHRISTOV
I don't know if code like this has been posted on this echo, but anyway here
it goes. It implements three different versions of Qsort which so far if the
fastest sorting algorithm known. However, it is not adequate For sorting File
Records. I've tested the routines and have worked With them For quite a While,
but don't trust me 8-) Murphy never sleeps 8-)
}
Unit SORT;
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
{ Purpose : Unit that implements a generic QSort(), similar to }
{ the one in the standard C library. }
{ Author : Alexander Christov }
{ Notes : Very instructive on the use of Pointers in TP. }
{ }
{ Use freely. }
{ }
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Interface
Type CmpFunc=Function(El1,El2:Pointer):Boolean;
Procedure QSort(Base:Pointer;Elements,Size:Word;GT:CmpFunc);
{ Base - Pointer to the first element
Elements - Number of elements
Size - Size of an element in Bytes. Use SizeOf() if in doubt
GT - A Function of Type CmpFunc that compares the elements pointed
to by the first and the second arguments and returns True
if the first is greater than the second. GT = Greater Than
8-)
}
{ Some commonly used CmpFunc }
Function bGT(El1,El2:Pointer):Boolean; { Compares ^Byte }
Function wGT(El1,El2:Pointer):Boolean; { Compares ^Word }
Function lGT(El1,El2:Pointer):Boolean; { Compares ^LongInt }
Function rGT(El1,El2:Pointer):Boolean; { Compares ^Real }
Implementation
{$F+}
Type Dummy=Array[0..0] of Byte;
pDummy=^Dummy;
{ Recursive Implementation }
Procedure _Sort(Base:Pointer;L,R,Size:Word;GT:CmpFunc);
Var I,J:Integer;
Var X:Pointer;
Procedure SwapElements(El1,El2:Word);
Var Tmp:Pointer;
begin
GetMem(Tmp,Size);
Move(pDummy(Base)^[El1*Size],Tmp^,Size);
Move(pDummy(Base)^[El2*Size],pDummy(Base)^[El1*Size],Size);
Move(Tmp^,pDummy(Base)^[El2*Size],Size);
FreeMem(Tmp,Size);
end;
begin
I:=L;
J:=R;
GetMem(X,Size);
Move(pDummy(Base)^[((L+R) div 2)*Size],X^,Size);
Repeat
While GT(X,@pDummy(Base)^[I*Size]) do INC(I);
While GT(@pDummy(Base)^[J*Size],X) do DEC(J);
if I<=J then begin
if I<>J then SwapElements(I,J);
INC(I);
DEC(J);
end;
Until I>J;
FreeMem(X,Size);
if L<J then _Sort(Base,L,J,Size,GT);
if I<R then _Sort(Base,I,R,Size,GT);
end;
Procedure QSort(Base:Pointer;Elements,Size:Word;GT:CmpFunc);
begin
_Sort(Base,0,Elements-1,Size,GT);
end;
Function bGT(El1,El2:Pointer):Boolean;
Type pByte=^Byte;
begin
bGt:=(pByte(El1)^>pByte(El2)^);
end;
Function wGT(El1,El2:Pointer):Boolean;
Type pWord=^Word;
begin
wGt:=(pWord(El1)^>pWord(El2)^);
end;
Function lGT(El1,El2:Pointer):Boolean;
Type pLongInt=^LongInt;
begin
lGt:=(pLongInt(El1)^>pLongInt(El2)^);
end;
Function rGT(El1,El2:Pointer):Boolean;
Type pReal=^Real;
begin
rGt:=(pReal(El1)^>pReal(El2)^);
end;
end.
{$A-,B-,D+,E-,F+,G+,I-,L+,N-,O+,P+,Q-,R-,S-,T-,V-,X+,Y+}
{ I don't know which settings are Really necessary For this Unit, but since
I always work With the above, I'm including them to make sure the Unit
compiles in your computer. The only critical ones (I Think) are R- and F+
}
Unit SORT;
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
{ Purpose: Unit that implements a generic QSort, similar to the }
{ one in the standard C library, but a lot more general }
{ This new version allows ordering of almost anything, }
{ even structures whose elements are not contiguous in memory }
{ or have strange mutual dependancies that don't allow "happy }
{ swapping". Obviously, this version is slower than the }
{ previous one. if you won't be sorting Linked Lists or }
{ Collections, use the previous one. }
{ Author : Alexander Christov }
{ Notes : Very instructive on the use of Pointers in TP. }
{ This version does not limit the number of elements to }
{ 65535 since the need not be contiguous. }
{ }
{ Use freely. }
{ }
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Interface
Type CmpFunc=Function(El1,El2:Pointer):Boolean;
AddrFunc=Function(Base:Pointer;Size,N:LongInt):Pointer;
SwapProc=Procedure(El1,El2:Pointer;Size:LongInt);
Procedure QSort(Base:Pointer; { Pointer to the first element.
if the user Writes his own GT, Addr and
Swap, this isn't Really necessary.
}
Elements:LongInt; { Total number of elements }
Size:Word; { Size of an element in Bytes }
GT:CmpFunc; { Comparing Function }
Addr:AddrFunc; { Addressing Function }
Swap:SwapProc); { Swapping Function }
{
GT - A funcion of Type CmpFunc that compares the elements pointed
to by its first and second arguments, and returns True if the
first element is Greater Than the second one. This Unit defines
some commonly used CmpFuncs:
bGT - Compares Bytes
wGT - Compares Words
lGT - Compares LongInts
rGT - Compares Reals
Addr - A Function that receives the index of an element and must
return a Pointer to it.
This Unit defines the Function
LinearAddr
which can be used whenever the elements are located
contiguously in memory.
Swap - A Procedure that swaps the elements pointed by its arguments.
DirectSwap
is defined in the Unit, which can be used whenever the elements
are mutually independent or no external processes are needed
when swapping two elements
}
{ Commonly used CmpFuncs }
Function bGT(El1,El2:Pointer):Boolean; { Compares ^Byte }
Function wGT(El1,El2:Pointer):Boolean; { Compares ^Word }
Function lGT(El1,El2:Pointer):Boolean; { Compares ^LongInt }
Function rGT(El1,El2:Pointer):Boolean; { Compares ^Real }
Function LinearAddr(Base:Pointer;Size,N:LongInt):Pointer;
Procedure DirectSwap(El1,El2:Pointer;Size:LongInt);
Implementation
{$F+}
Type Dummy=Array[0..0] of Byte;
pDummy=^Dummy;
Var X,Middle:Pointer;
Procedure
_Sort(Base:Pointer;L,R:LongInt;Size:Word;GT:CmpFunc;Addr:AddrFunc;Swap:SwapProc
);
Var I,J:LongInt;
begin
I:=L;
J:=R;
Move(Addr(Base,Size,(L+R) div 2)^,Middle^,Size);
Repeat
While GT(Middle,Addr(Base,Size,I)) do INC(I);
While GT(Addr(Base,Size,J),Middle) do DEC(J);
if I<=J then begin
if I<>J then Swap(Addr(Base,Size,I),Addr(Base,Size,J),Size);
INC(I);
DEC(J);
end;
Until I>J;
if L<J then _Sort(Base,L,J,Size,GT,Addr,Swap);
if I<R then _Sort(Base,I,R,Size,GT,Addr,Swap);
end;
Procedure QSort;
begin
GetMem(X,Size); { <- Made in Arturo Ramirez 8-) }
GetMem(Middle,Size);
_Sort(Base,0,Elements-1,Size,GT,Addr,Swap);
FreeMem(X,Size);
FreeMem(Middle,Size);
end;
Function bGT(El1,El2:Pointer):Boolean;
Type pByte=^Byte;
begin
bGt:=(pByte(El1)^>pByte(El2)^);
end;
Function wGT(El1,El2:Pointer):Boolean;
Type pWord=^Word;
begin
wGt:=(pWord(El1)^>pWord(El2)^);
end;
Function lGT(El1,El2:Pointer):Boolean;
Type pLongInt=^LongInt;
begin
lGt:=(pLongInt(El1)^>pLongInt(El2)^);
end;
Function rGT(El1,El2:Pointer):Boolean;
Type pReal=^Real;
begin
rGt:=(pReal(El1)^>pReal(El2)^);
end;
{ Linear Addressing }
Function LinearAddr;
begin
LinearAddr:=@pdummy(Base)^[N*Size];
end;
{ Direct swapping of elements. With the use of Addr() it is quite more
legible 8-) }
Procedure DirectSwap;
Var Tmp:Pointer;
begin
GetMem(Tmp,Size);
Move(El1^,Tmp^,Size);
Move(El2^,El1^,Size);
Move(Tmp^,El2^,Size);
FreeMem(Tmp,Size);
end;
end.
{ And finally a specific version of QSort() written in Assembler. It is
non recursive and sorts Arrays of Words of up to 16383 elements (since
it Uses the addresses of the elements rather than their indexes, and since
SizeOf(Word)=2 -> 16384*2=32768 "=" -32768, and the routine Uses signed
comparisons between adresses.
On my 386/33 it sorts 10 times an Array of 10000 Words in 3.6 sec, While
the first QSort() does the same in 46 sec.
Must be called With
Qsort(Pointer to the first element, 0, elements-1)
Use freely. if you include the source directly in your Program, credit
must be given.
}
Procedure QSort(Base:Pointer;L,R:Word);Assembler;
Var TmpL,TmpR,TmpDI:Word;
Asm
xor AX,AX
PUSH AX
PUSH AX { 0 0 will act as a flag on the stack indicating that no more }
PUSH R { (L,R) pairs need to be sorted }
PUSH L
@MainLoop:
LES DI,Base
MOV TmpDI,DI
xor SI,SI
MOV BX,DI
POP AX { AX<-L }
MOV TmpL,AX
MOV SI,AX
SHL AX,1
ADD DI,AX
POP AX { AX<-R }
MOV TmpR,AX
and AX,AX { R can be never 0 except if this is the (0,0) flag }
JZ @end
ADD SI,AX
SHL AX,1
ADD BX,AX
and SI,$FFFE
ADD SI,TmpDI
{ ES:DI -> Element[I] (L)
ES:BX -> Element[J] (R)
ES:SI -> Element[(L+R) div 2]
}
MOV AX,ES:[SI]
@Loop1:
MOV CX,ES:[DI]
CMP AX,CX
JNA @Loop2
ADD DI,2
JMP @Loop1
@Loop2:
MOV CX,ES:[BX]
CMP CX,AX
JNA @Check
SUB BX,2
JMP @Loop2
@Check:
CMP DI,BX
JG @Cont1
MOV CX,ES:[DI]
MOV DX,ES:[BX]
MOV ES:[DI],DX
MOV ES:[BX],CX
ADD DI,2
SUB BX,2
CMP DI,BX
JNG @Loop1
@Cont1:
SUB DI,TmpDI
SAR DI,1 { DI - I }
SUB BX,TmpDI
SAR BX,1 { BX - J }
CMP DI,TmpR
JGE @Cont2
PUSH TmpR { I<R }
PUSH DI
@Cont2:
CMP TmpL,BX
JGE @MainLoop
PUSH BX { L<J }
PUSH TmpL
JMP @MainLoop
@end:
end;
{ --------------------------- CUT ----------------------------}
(*
From: ROLAND WODITSCH
Subj: QUICK SORT
*)
UNIT QSort5;
INTERFACE
TYPE OrdFunction = FUNCTION(VAR a,b):BOOLEAN;
PROCEDURE Sortiere(VAR SortArray; Elementgroesse,LoIndex,HiIndex: word;
SortKleiner: OrdFunction; von,bis:word);
{ SortArray field to sort }
{ LoIndex the lowest, }
{ HiIndex the highest fieldindex like in the fielddeklarartion }
{ OrdAdr the funktion from typ OrdFunction (s.o.) }
{ von, bis the sortarea }
{ befor calling (not befor bind!) your have to define a }
{ asymmetric order funktion : }
{ function IrgendEinName(VAR x,y : TypDerFeldElemente):boolean }
{ example: (*$F+*) function kleiner(VAR x,y: integer):boolean; }
{ begin kleiner:=x<y end; (*$F-*) }
{ not: kleiner:=x<=y (not asymmetric!) }
{ attention: x and y must be VAR-parameters !!! }
IMPLEMENTATION
procedure Sortiere(VAR SortArray; ElementGroesse,LoIndex,HiIndex: word;
SortKleiner:OrdFunction; von,bis:word);
type ArrayPtr = ^Byte;
var Mitte, i0, j0, m0 : ArrayPtr;
procedure Swap(VAR x,y; size : word);
begin
INLINE ($1E/$C4/$B6/X/$C5/$BE/Y/$8B/$8E/SIZE/$E3/$0C/$26/$8A/$04/
$86/$05/$26/$88/$04/$46/$47/$E2/$F4/$1F)
end;
function Element(i : word) : ArrayPtr;
begin
Element:=ptr(seg(SortArray),ofs(SortArray)+i*ElementGroesse)
end;
procedure inc(var index : word; var pointer : ArrayPtr);
begin
index:=succ(index);
pointer:=ptr(seg(pointer^),ofs(pointer^)+ElementGroesse)
end;
procedure dec(var index : word; var pointer : ArrayPtr);
begin
index:=pred(index);
pointer:=ptr(seg(pointer^),ofs(pointer^)-ElementGroesse)
end;
procedure E_Sort(von, bis : word);
label EXIT;
var i, j : word;
begin
if bis<=von then goto EXIT;
i:=von; i0:=Element(i);
while i<bis do begin
m0:=i0; j:=i; j0:=i0; inc(j,j0);
while j<=bis do begin
if SortKleiner(j0^,m0^) then m0:=j0;
inc(j,j0)
end; (* WHILE j *)
if m0<>i0 then Swap(i0^,m0^,ElementGroesse);
inc(i,i0)
end; (* WHILE i *)
EXIT:
end; (* E_Sort *)
procedure Sort(von, bis : word); (* Rekursive Quicksort *)
label EXIT;
var i, j : word;
begin
if bis-von<6 then begin E_Sort(von,bis); goto EXIT end;
i:=von; j:=bis; m0:=Element((i+j) SHR 1);
move(m0^,Mitte^,ElementGroesse); i0:=Element(i); j0:=Element(j);
while i<=j do begin
while SortKleiner(i0^,Mitte^) do inc(i,i0);
while SortKleiner(Mitte^,j0^) do dec(j,j0);
if i<=j then begin
if i<>j then Swap(i0^,j0^,ElementGroesse);
inc(i,i0); dec(j,j0)
end (* if i<=j *)
end; (* while i<=j *)
if bis-i<j-von then begin
if i<bis then Sort(i,bis);
if von<j then Sort(von,j)
end
else begin
if von<j then Sort(von,j);
if i<bis then Sort(i,bis)
end;
EXIT:
end; (* Sort *)
begin
getmem(Mitte,ElementGroesse);
Sort(von-LoIndex,bis-LoIndex);
freemem(Mitte,ElementGroesse)
end; (* Sort *)
END. (* IMPLEMENTATION OF UNIT QSORT *)
{ --------------------------- CUT ----------------------------}
unit Qsort;
{TQSort by Mike Junkin 10/19/95.
DoQSort routine adapted from Peter Szymiczek's QSort procedure which
was presented in issue#8 of The Unofficial Delphi Newsletter.}
interface
uses
SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
Forms, Dialogs;
type
TSwapEvent = procedure (Sender : TObject; e1,e2 : word) of Object;
TCompareEvent = procedure (Sender: TObject; e1,e2 : word; var Action : integer) of Object;
TQSort = class(TComponent)
private
FCompare : TCompareEvent;
FSwap : TSwapEvent;
public
procedure DoQSort(Sender: TObject; uNElem: word);
published
property Compare : TCompareEvent read FCompare write FCompare;
property Swap : TSwapEvent read FSwap write FSwap;
end;
procedure Register;
implementation
procedure Register;
begin
RegisterComponents('Mikes', [TQSort]);
end;
procedure TQSort.DoQSort(Sender: TObject; uNElem: word);
{ uNElem - number of elements to sort }
procedure qSortHelp(pivotP: word; nElem: word);
label
TailRecursion,
qBreak;
var
leftP, rightP, pivotEnd, pivotTemp, leftTemp: word;
lNum: word;
retval: integer;
begin
retval := 0;
TailRecursion:
if (nElem <= 2) then
begin
if (nElem = 2) then
begin
rightP := pivotP +1;
FCompare(Sender,pivotP,rightP,retval);
if (retval > 0) then Fswap(Sender,pivotP,rightP);
end;
exit;
end;
rightP := (nElem -1) + pivotP;
leftP := (nElem shr 1) + pivotP;
{ sort pivot, left, and right elements for "median of 3" }
FCompare(Sender,leftP,rightP,retval);
if (retval > 0) then Fswap(Sender,leftP, rightP);
FCompare(Sender,leftP,pivotP,retval);
if (retval > 0) then Fswap(Sender,leftP, pivotP)
else
begin
FCompare(Sender,pivotP,rightP,retval);
if retval > 0 then Fswap(Sender,pivotP, rightP);
end;
if (nElem = 3) then
begin
Fswap(Sender,pivotP, leftP);
exit;
end;
{ now for the classic Horae algorithm }
pivotEnd := pivotP + 1;
leftP := pivotEnd;
repeat
FCompare(Sender,leftP, pivotP,retval);
while (retval <= 0) do
begin
if (retval = 0) then
begin
Fswap(Sender,leftP, pivotEnd);
Inc(pivotEnd);
end;
if (leftP < rightP) then
Inc(leftP)
else
goto qBreak;
FCompare(Sender,leftP, pivotP,retval);
end; {while}
while (leftP < rightP) do
begin
FCompare(Sender,pivotP, rightP,retval);
if (retval < 0) then
Dec(rightP)
else
begin
FSwap(Sender,leftP, rightP);
if (retval <> 0) then
begin
Inc(leftP);
Dec(rightP);
end;
break;
end;
end; {while}
until (leftP >= rightP);
qBreak:
FCompare(Sender,leftP,pivotP,retval);
if (retval <= 0) then Inc(leftP);
leftTemp := leftP -1;
pivotTemp := pivotP;
while ((pivotTemp < pivotEnd) and (leftTemp >= pivotEnd)) do
begin
Fswap(Sender,pivotTemp, leftTemp);
Inc(pivotTemp);
Dec(leftTemp);
end; {while}
lNum := (leftP - pivotEnd);
nElem := ((nElem + pivotP) -leftP);
if (nElem < lNum) then
begin
qSortHelp(leftP, nElem);
nElem := lNum;
end
else
begin
qSortHelp(pivotP, lNum);
pivotP := leftP;
end;
goto TailRecursion;
end; {qSortHelp }
begin
if Assigned(FCompare) and Assigned(FSwap) then
begin
if (uNElem < 2) then exit; { nothing to sort }
qSortHelp(1, uNElem);
end;
end; { QSort }
end.
{ demo }
unit Unit1;
interface
uses
SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
Forms, Dialogs, Grids, Qsort, StdCtrls;
type
TForm1 = class(TForm)
QSort1: TQSort;
StringGrid1: TStringGrid;
Button1: TButton;
procedure FormCreate(Sender: TObject);
procedure QSort1Compare(Sender: TObject; e1, e2: Word; var Action: Integer);
procedure QSort1Swap(Sender: TObject; e1, e2: Word);
procedure Button1Click(Sender: TObject);
end;
var
Form1: TForm1;
implementation
{$R *.DFM}
procedure TForm1.FormCreate(Sender: TObject);
begin
with StringGrid1 do
begin
Cells[1,1] := 'the';
Cells[1,2] := 'brown';
Cells[1,3] := 'dog';
Cells[1,4] := 'bit';
Cells[1,5] := 'me';
end;
end;
procedure TForm1.QSort1Compare(Sender: TObject; e1, e2: Word;
var Action: Integer);
begin
with Sender as TStringGrid do
begin
if (Cells[1, e1] < Cells[1, e2]) then
Action := -1
else if (Cells[1, e1] > Cells[1, e2]) then
Action := 1
else
Action := 0;
end; {with}
end;
procedure TForm1.QSort1Swap(Sender: TObject; e1, e2: Word);
var
s: string[63]; { must be large enough to contain the longest string in the grid }
i: integer;
begin
with Sender as TStringGrid do
for i := 0 to ColCount -1 do
begin
s := Cells[i, e1];
Cells[i, e1] := Cells[i, e2];
Cells[i, e2] := s;
end; {for}
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
QSort1.DoQSort(StringGrid1,STringGrid1.RowCount-1);
end;
end.
{ --------------------------- CUT ----------------------------}
{
> Could someone please post some code on using a quick
> sort to sort an array of strings?
I can do even better than that. I can give you some code on a general qsort
routine that works like in C (if you're familiar with that). I. e. you can sort
any type of arrays, if only you supply the correct compare function. Here
goes...
}
unit QSort;
{*********************************************************
* QSORT.PAS *
* C-like QuickSort implementation *
* Written 931118 by Bj�rn Felten @ 2:203/208 *
* After an idea by Pontus Rydin *
*********************************************************}
interface
type CompFunc = function(Item1, Item2 : word) : integer;
procedure QuickSort(
var Data;
{An array. Must be [0..Count-1] and not [1..Count] or anything else! }
Count,
{Number of elements in the array}
Size : word;
{Size in bytes of a single element -- e.g. 2 for integers or words,
4 for longints, 256 for strings and so on }
Compare : CompFunc);
{The function that decides which element is "greater" or "less". Must
return an integer that's < 0 if the first element is less, 0 if they're
equal and > 0 if the first element is greater. A simple Compare for
words can look like this:
function WordCompare(Item1, Item2: word): integer;
begin
WordCompare := MyArray[Item1] - MyArray[Item2]
end;
NB. It's not the =indices= that shall be compared, it's the elements that
the supplied indices points to! Very important to remember!
Also note that the array may be sorted in descending order just by
means of a simple swap of Item1 and Item2 in the example.}
implementation
procedure QuickSort;
procedure Swap(Item1, Item2 : word);
var P1, P2 : ^byte; I : word;
begin
if Item1 <> Item2 then
begin
I := Size;
P1 := @Data; inc(P1, Item1 * Size);
P2 := @Data; inc(P2, Item2 * Size);
asm
mov cx,I { Size }
les di,P1
push ds
lds si,P2
@L:
mov ah,es:[di]
lodsb
mov [si-1],ah
stosb
loop @L
pop ds
end
end
end;
procedure Sort(Left, Right: integer);
var i, j, x, y : integer;
begin
i := Left; j := Right; x := (Left+Right) div 2;
repeat
while compare(i, x) < 0 do inc(i);
while compare(x, j) < 0 do dec(j);
if i <= j then
begin
swap(i, j); inc(i); dec(j)
end
until i > j;
if Left < j then Sort(Left, j);
if i < Right then Sort(i, Right)
end;
begin Sort(0, Count) end;
end. { of unit }
{ A simple testprogram can look like this: }
program QS_Test; {Test QuickSort � la C}
uses qsort;
var v: array[0..9999] of word;
i: word;
{$F+} {Must be compiled as FAR calls!}
function cmpr(a, b: word): integer;
begin cmpr := v[a] - v[b] end;
function cmpr2(a, b: word): integer;
begin cmpr2 := v[b] - v[a] end;
{$F-}
begin
randomize;
for i := 0 to 9999 do v[i] := random(20000);
quicksort(v, 10000, 2, cmpr); {in order lo to hi}
quicksort(v, 10000, 2, cmpr2); {we now have a sorted list, sort it in
{reverse -- nasty for qsort!}
quicksort(v, 10000, 2, cmpr); {and reverse again}
quicksort(v, 10000, 2, cmpr); {sort a sorted list -- also not very popular}
end.
{ --------------------------- CUT ----------------------------}
{************************************************}
{ }
{ QuickSort Demo }
{ Copyright (c) 1985,90 by Borland International } { und: Robert Beicht ;-) }
{ }
{************************************************}
program QSort;
{$R-,S-}
uses Crt;
{ This program demonstrates the quicksort algorithm, which }
{ provides an extremely efficient method of sorting arrays in }
{ memory. The program generates a list of 1000 random numbers }
{ between 0 and 29999, and then sorts them using the QUICKSORT }
{ procedure. Finally, the sorted list is output on the screen. }
{ Note that stack and range checks are turned off (through the }
{ compiler directive above) to optimize execution speed. }
const
Max = 100;
type { ***** }
PData = ^TData; { ***** }
TData = record { ***** }
NachName: String[25]; { ***** }
VorName: String[25]; { ***** }
{..} { ***** }
end; { ***** }
List = array[1..Max] of TData;
var
Data: List;
I: Integer;
function Less(var d1,d2:TData): Boolean; { ***** }
begin { ***** }
if d1.NachName < d2.NachName then Less := True else { ***** }
if d1.NachName > d2.NachName then Less := False else { ***** }
if d1.VorName < d2.VorName then Less := True else { ***** }
if d1.VorName > d2.VorName then Less := False else Less := False; { ***** }
end; { ***** }
{ QUICKSORT sorts elements in the array A with indices between }
{ LO and HI (both inclusive). Note that the QUICKSORT proce- }
{ dure provides only an "interface" to the program. The actual }
{ processing takes place in the SORT procedure, which executes }
{ itself recursively. }
procedure QuickSort(var A: List; Lo, Hi: Integer);
procedure Sort(l, r: Integer);
var
i, j, x: integer; { ***** }
y: TData; { ***** }
begin
i := l; j := r; x := (l+r) DIV 2;
repeat
while Less(a[i], a[x]) do i := i + 1; { ***** }
while Less(a[x], a[j]) do j := j - 1; { ***** }
if i <= j then
begin
y := a[i]; a[i] := a[j]; a[j] := y;
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 {QuickSort};
Sort(Lo,Hi);
end;
begin {QSort}
(*Initialisiere List*)
Sort(List, 1, Count);
end.
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