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x_sanctus
Member
Joined: 02 Mar 2005
Posts: 4
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 Posted: 07/03/05 13:45 Post subject: beginner class linked list in delphi |
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| is there any linked list in delphi? or i have to create in myself? |
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Stefan
Junior Member
Joined: 27 Sep 2004
Posts: 61
Location: Netherlands
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| Posted: 07/03/05 14:35 Post subject: |
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Hi,
See this site for a Double Linked list implementation.
See this site for a LIFO stack using a linked list...
Good luck,
Stefan |
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x_sanctus
Member
Joined: 02 Mar 2005
Posts: 4
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| Posted: 08/03/05 11:47 Post subject: |
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| Stefan wrote: | Hi,
See this site for a Double Linked list implementation.
See this site for a LIFO stack using a linked list...
Good luck,
Stefan |
hi
i still got a problem i make linked list just like this:
unit ulist;
interface
uses
Windows;
type
PSimpulNode =^TSimpulNode;
Simpul = record
ns :integer;
P : TPoint;
end;
TSimpulNode =record
Next : PSimpulNode;
Info : Simpul;
end;
var
FirstSimpul : PSimpulNode;
procedure AllocNodeSimpul(item :PSimpulNode; ns:integer; P:TPoint);
procedure insertLastSimpul(no : integer; P:TPoint);
implementation
procedure AllocNodeSimpul(item :PSimpulNode;ns:integer;P:TPoint);
begin
New(Item);
Item^.Info.ns:=ns;
Item^.Info.P:=P;
Item^.Next:=nil;
end;
procedure insertLastSimpul(no : integer; P:TPoint);
var
TempNode: PSimpulNode;
newSimpul : PSimpulNode;
begin
AllocNodeSimpul(newSimpul,no,P);
TempNode := FirstSimpul;
while TempNode^.Next <> nil do
begin
TempNode := TempNode^.Next;
end;
TempNode^.Next:=newSimpul;
end;
end.
the procedure insertLastSimpul just dont work. when i call it
error i got messagge access violation at address 000000000. Since i don't familiar with delphi syntax. is there anything wrong in my program? please help... |
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Stefan
Junior Member
Joined: 27 Sep 2004
Posts: 61
Location: Netherlands
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| Posted: 08/03/05 12:49 Post subject: |
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Hi,
please try the following...
Replace insertLastSimpul with:
| Code: |
procedure insertLastSimpul(no : integer; P:TPoint);
var
TempNode: PSimpulNode;
newSimpul : PSimpulNode;
begin
GetMem(newSimpul, SizeOf(TSimpulNode));
AllocNodeSimpul(newSimpul,no,P);
TempNode := @FirstSimpul;
while TempNode^.Next <> nil do
TempNode := TempNode^.Next;
TempNode^.Next:=newSimpul;
end;
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if you don't, Delphi gives a warning "Variable newSimpul might not have been initialized"
I've also replaced the global var FirstSimpul:
| Code: |
var
FirstSimpul : TSimpulNode;
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Hope this helps
Stefan |
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x_sanctus
Member
Joined: 02 Mar 2005
Posts: 4
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| Posted: 09/03/05 11:17 Post subject: |
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| Stefan wrote: | Hi,
please try the following...
Replace insertLastSimpul with:
| Code: |
procedure insertLastSimpul(no : integer; P:TPoint);
var
TempNode: PSimpulNode;
newSimpul : PSimpulNode;
begin
GetMem(newSimpul, SizeOf(TSimpulNode));
AllocNodeSimpul(newSimpul,no,P);
TempNode := @FirstSimpul;
while TempNode^.Next <> nil do
TempNode := TempNode^.Next;
TempNode^.Next:=newSimpul;
end;
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if you don't, Delphi gives a warning "Variable newSimpul might not have been initialized"
I've also replaced the global var FirstSimpul:
| Code: |
var
FirstSimpul : TSimpulNode;
|
Hope this helps
Stefan |
that was really great help. thanks
but i still get stuck here
hope you don't mind
i have diffrent list
| Code: |
unit ulist;
interface
uses Windows;
type
PSisiNode=^TSisiNode;
Sisi = record
aw : integer;
ak : integer;
s : integer;
v : integer;
d : real;
end;
TSisiNode =record
Next : PSisiNode;
Info : Sisi;
end;
var FirstSisi : TSisiNode;
procedure AllocNodeSisi(item :PSisiNode;aw:integer;ak:integer;
s:integer; v:integer);
function getDelay(s: integer; v: integer): real;
procedure insertSisi(aw: integer; ak:integer; s:integer ; v: integer);
procedure DeleteAllSisiSimpul(no:integer);
implementation
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but i still got problem in insertSisi() and DeleteAll sisi() procedure. when i call it my program hang and still don't understand why can i happened.
Please help.....
| Code: |
procedure AllocNodeSisi(item :PSisiNode;aw:integer;ak:integer;
s:integer; v:integer);
begin
New(item);
item^.Next:=nil;
item^.Info.aw:=aw;
item^.Info.ak:=ak;
item^.Info.s:=s;
item^.Info.v:=v;
item^.Info.d:=getDelay(s,v);
end;
function getDelay(s: integer; v: integer): real;
begin
getDelay:=s/v;
end;
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| Code: |
procedure insertSisi(aw: integer; ak:integer; s:integer ; v: integer);
var
Temp:PSisiNode;
found:boolean;
newSisiNode : PSisiNode;
begin
GetMem(newSisiNode, SizeOf(TSisiNode));
AllocNodeSisi(newSisiNode,aw,ak,s,v);
Temp:=@FirstSisi;
found:=false;
if(FirstSisi.Info.aw<>0) then
begin
while((not found) or (aw <= Temp^.Info.aw) or (Temp<>nil) ) do
begin
if((aw=Temp^.Info.aw) and (ak > Temp^.Info.ak)) then
found:=true
else
Temp:=Temp^.Next;
end;
if (found) then //insert after
begin
newSisiNode^.Next:=Temp^.Next;
Temp^.Next:=newSisiNode;
end
else //insert last
Temp^.Next:=newSisiNode;
end
else //insert first
begin
newSisiNode^.next:=@FirstSisi;
FirstSisi:=newSisiNode^;
end;
end;
procedure DeleteAllSisiSimpul(no:integer);
//delete all sisi which aw=no
var
temp:PSisiNode;
prev:PSisiNode;
pdel:PSisiNode;
begin
temp:=@FirstSisi;
//traversal list
if(temp^.Next<>nil) then
begin
while(((temp^.next).Info.aw <> no) and (temp<>nil )) do
temp:=temp^.Next;
prev:=temp;
//deleting
while((temp.Info.aw=no )or(temp.Next<>nil)) do
begin
pdel:=temp;
Dispose(pdel);
temp:=temp^.Next;
end;
prev^.Next:=temp;
end
else
begin
if(FirstSisi.Info.aw=no) then
begin
Dispose(@FirstSisi);
end;
end;
end;
end.
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Stefan
Junior Member
Joined: 27 Sep 2004
Posts: 61
Location: Netherlands
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| Posted: 09/03/05 13:02 Post subject: |
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There's a couple of problems in the code:
getDelay could return with an invalid floatingpoint operation...
| Code: |
function getDelay(s: integer; v: integer): real;
begin
if (s > 0) and (v > 0) then
getDelay:=s/v
else
getDelay:=0;
end;
|
Instead of using GetMem use New instead (sorry  ):
| Code: |
procedure insertSisi(aw: integer; ak:integer; s:integer ; v: integer);
...
begin
New(newSisiNode);
AllocNodeSisi(newSisiNode,aw,ak,s,v);
...
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And leave the New() call out of AllocNodeSisi().
I'd change the FirstSisi back to PSisiNode instead of TSisiNode. That will make it initialize to nil and you can check for that in the insertSisi() procedure:
| Code: |
if Assigned(FirstSisi) then begin
if(FirstSisi^.Info.aw<>0) then begin
....
else
FirstSisi := newSisiNode;
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That way you will not get an access violation when you try to address it here:
| Code: |
if(FirstSisi^.Info.aw<>0) then begin
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In the following part you might get stuck in an endless loop:
| Code: |
while ((not found) or (aw <= Temp^.Info.aw) or (Temp<>nil) ) do begin
if((aw=Temp^.Info.aw) and (ak > Temp^.Info.ak)) then
found:=true
else
Temp:=Temp^.Next;
endd;
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if it's called like this:
| Code: |
InsertSisi(1, 1, 1, 1);
InsertSisi(1, 2, 3, 4);
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FirstSisi's aw=1 and ak=1
SecondNode's aw=1 and ak=2 putting you in an endless loop. Remember:
if((aw=Temp^.Info.aw) and (ak > Temp^.Info.ak)) then
found := true;
This will make found = true but this:
while ((not found) or (aw <= Temp^.Info.aw) or (Temp<>nil) ) do begin
will just not care because Temp<>nil (it's got the pointer to FirstSisi) and aw <= Temp^.Info.aw is also true because aw of the second node =1 and FirstSisi's aw=1...
Maybe use a Break in the while loop:
| Code: |
while ((not found) or (aw <= Temp^.Info.aw) or (Temp<>nil) ) do begin
if((aw=Temp^.Info.aw) and (ak > Temp^.Info.ak)) then begin
found:=true;
break;
end else
Temp:=Temp^.Next;
end;
|
Please work this out first
Stefan |
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