Double linked list c8
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This document discusses the Pascal programming language and some of its key features including sets, records, files, pointers, linked lists, and units. It then focuses on describing the structure of a doubly linked list in Pascal which includes the data type, references to the next and previous elements, and examples of inserting and deleting elements from the list. Procedures are provided for inserting elements into the list in different locations and deleting elements from the start, end, or middle of the list.
Double linked list c8
- 1. Pascal Programming Language Omar ElSabek & Fayez Ghazzawi IT Engineering 3th year – UNKNOWN Department programming II
- 2. Sets Record Files (Text & Binary) Pointers Linked Lists Unit Course Index :
- 4. It has three elements: 1. The Variable(s) with Data type(s) “the same with all the Linked List elements”. 2. The References which refers to the next element in the Linked List This Reference has the value of (nil) in the last element in the Linked List. 3. The References which refers to the previous element in the Linked List This Reference has the value of (nil) in the first element in the Linked List.
- 5. Program test1; Type D_P = ^D_R; D_R = record num : integer; next,prev : D_P; end; Now let’s meet with some procedures which are used in DLL
- 6. It has three cases: 1. Insert an element in the first of DLL 2. Insert an element in the last of DLL 3. Insert an element anywhere else
- 7. Procedure Insert (var L_S,L_E: D_P; numb: integer) Var S,temp : D_P; located : boolean Begin new(temp); temp^.num := numb; temp^.next := nil; temp^.prev := nil; if (L_S = nil) then begin L_S := temp; L_E := temp; end
- 8. else begin S := L_S; located := false; while (S <> nil) and (not located) do begin if (S^.num < numb) then S := S^.next; else located := true; end; temp^.next := S;
- 9. if (L_S = S) then begin L_S^.prev := temp; L_S := temp; end else if (S = nil) then begin L_E^.next := temp; temp^.prev := L_E; L_E := temp; end
- 10. else begin S^.prev^.next := temp; temp^.prev := S^.prev; S^.prev := temp; end; end; End;
- 11. It has three cases: 1. Delete the first element 2. Delete the last element 3. Delete any other element
- 12. Procedure Delete(var L_S,L_E: D_P; numb: integer; flag: char) Var S,temp : D_P; Begin if (L_S = nil) then flag := ‘0’; if (numb = L_S^.num) then begin flag := ‘1’; temp := L_S; L_S := L_S^.next; L_S^.prev := nil; dispose(temp); end
- 13. else if (numb = L_E^.num) then begin flag := ‘1’; temp := L_E; L_E := L_E^.prev; L_E^.next := nil; dispose(temp); end
- 14. else begin S := L_S; while (S <> nil) and (S^.num <> numb) do S := S^.next if (S = nil) then flag := ‘2’ else begin flag := ‘1’; S^.next^.prev := S^.prev; S^.prev^.next := S^.next; dispose(S); end; end; End;