1. LAB#4

2. Linked List : A linked list is a series of connected nodes. Each node contains at least: – A piece of data (any type) – Pointer to the next node in the list Head: pointer to the first node. The last node points to NULL. A 0 Head BCA datapointer node Tail

3. SinglyLinked List : Singly Linked List : We use two classes: Node and List o Declare IntSLLNode class for the nodes class IntSLLNode { public: IntSLLNode() { next = 0; } IntSLLNode(int i, IntSLLNode *ptr = 0) { info = i; next = ptr; } int info; IntSLLNode *next; };

4. SinglyLinked List : Singly Linked List : o Declare IntSLList which contains : class IntSLList { public: IntSLList() {head = tail =0; } void AddToHead(int); void AddToTail(int); void DeleteFromHead(); void DeleteFromTail(); void DeleteNode(int); bool isInList(int) const; void DisplayList(); private: IntSLLNode *head, *tail; };

5. Linked Lists5 Inserting at the Head 1.Allocate a new node 2.Insert new element 3.Make new node point to old head 4.Update head to point to new node

6. SinglyLinked List : Singly Linked List : o Declare IntSLList Class member function: 1- void AddToHead(int); void IntSLList::AddToHead(int el) { head = new IntSLLNode(el,head); if (tail == 0) tail = head; }

7. Linked Lists7 Inserting at the Tail 1. Allocate a new node 2. Insert new element 3. Have new node point to null 4. Have old last node point to new node 5. Update tail to point to new node

8. SinglyLinked List : Singly Linked List : o Declare IntLList Class member function: 2- void AddToTail(int); void IntSLList::AddToTail(int el) { if (tail != 0) // if list not empty; { tail->next = new IntSLLNode(el); tail = tail->next; } else head = tail = new IntSLLNode(el); }

9. Linked Lists9 Removing at the Head 1.Update head to point to next node in the list 2.Allow garbage collector to reclaim the former first node

10. SinglyLinked List : Singly Linked List : o Declare IntLList Class member function: 3- void DeleteFromHead(); void IntSLList::DeleteFromHead(){ if(head !=0) { IntSLLNode *tmp =head; if (head == tail) //if only one node in the list head = tail = 0; else head = head ->next; delete tmp;} }

11. Linked Lists11 Removing at the Tail Removing at the tail of a singly linked list cannot be efficient! There is no constant- time way to update the tail to point to the previous node

12. SinglyLinked List : Singly Linked List : 4- void DeleteFromTail(); void IntSLList::DeleteFromTail() {if(head != 0) {if (head == tail) //if only one node in the list {delete head; head=tail=0;} else { IntSLLNode *tmp; //find the predecessor of tail for(tmp=head; tmp->next != tail; tmp = tmp->next); delete tail; tail=tmp; tail->next=0;}} }

13. SinglyLinked List : Singly Linked List : o Declare IntLList Class member function: 5- int DeleteNode(int el);

15. SinglyLinked List : Singly Linked List : o Declare IntLList Class member function: 6- bool isInList(int) const; bool IntSLList:: isInList(int el) const { IntSLLNode *tmp; for (tmp=head; tmp != 0 && !(tmp->info == el); tmp = tmp->next); return tmp !=0; }

16. SinglyLinked List : Singly Linked List : o Declare IntSLList Class member function: 7- void DisplayList(); void IntSLList::DisplayList() {IntSLLNode *current; current = head; cout << "head = " << head << "\n"; while(current != 0) {cout info << " " << current << "\n"; current=current->next;} cout << "tail = " << tail << "\n"; cout << "----------------------" << "\n";}

17. SinglyLinked List : Singly Linked List : Using List : void main() {IntSLList myllist; myllist.AddToHead(50); myllist.AddToHead(90); myllist.AddToHead(60); myllist.AddToHead(68); myllist.DisplayList(); myllist.DeleteFromHead(); myllist.DeleteNode(60); if (myllist.isInList(60)== 0) cout<<"60 isn't in the list" << endl; cout<<"60 is in the list" << endl; myllist.DisplayList();}

18. Linked Lists18 Doubly Linked List A doubly linked list is often more convenient! Nodes store: – element – link to the previous node – link to the next node Special trailer and header nodes prevnext elem trailer header nodes/positions elements node

19. DoublyLinked List : Doubly Linked List : o Declare IntDLLNode which contains : class IntDLLNode{ public: IntDLLNode() {next=prev=0;} IntDLLNode(int el,IntDLLNode *n=0,IntDLLNode *p=0){ info = el; next=n; prev =p; } Int info; IntDLLNode *next, *prev; };

20. DoublyLinked List : Doubly Linked List : o Declare IntDLList which contains : class IntDLList{ public: IntDLList(){ Head=tail=0;} void addToDLLTail(int el); void deleteFromDLLTail(); void IntDLList::DisplayFromHead(); protected: IntDLLNode *head,*tail; };

21. Linked Lists21 Insertion We visualize operation insertAfter(p, X), which returns position q ABXC ABC p ABC p X q pq

22. Linked Lists22 Insertion Algorithm Algorithm insertAfter(p,e): Create a new node v v.setElement(e) v.setPrev(p){link v to its predecessor} v.setNext(p.getNext()){link v to its successor} (p.getNext()).setPrev(v){link p’s old successor to v} p.setNext(v){link p to its new successor, v} return v{the position for the element e}

23. DoublyLinked List : Doubly Linked List : o Declare IntDLList Class member function: 1- void addToDLLTail(int el); void IntDLList:: addToDLLTail(int el) {if (tail!=0){ tail=new IntDLLNode(el,0,tail); tail->prev->next=tail;} else head=tail=new IntDLLNode(el); }

24. Linked Lists24 Deletion We visualize remove(p), where p == last() ABCD p ABC D p ABC

25. Linked Lists25 Deletion Algorithm Algorithm remove(p): t = p.element{a temporary variable to hold the return value} (p.getPrev()).setNext(p.getNext()){linking out p} (p.getNext()).setPrev(p.getPrev()) p.setPrev(null){invalidating the position p} p.setNext(null) return t

26. DoublyLinked List : Doubly Linked List : o Declare IntDLList Class member function: 2- void deleteFromDLLTail() void IntDLList:: deleteFromDLLTail() {if(tail !=0){ if(head==tail) { //if only one node in the list delete head; head = tail =0;} else { tail = tail->prev; delete tail->next; tail->next = 0;}}}

27. DoublyLinked List : Doubly Linked List : o Declare IntDLList Class member function: 2- void IntDLList::DisplayFromHead(); void IntDLList::DisplayFromHead() { IntDLLNode *current; for( current = head ; current != 0 ; current = current->next ) cout info<<endl; cout<<"--------------------------------"<<endl; }

28. Exercise # 1: Complete, compile and run the following program. #include using namespace std; //------ class IntSLLNode for creating new node ---------------// class IntSLLNode { public: IntSLLNode() { next = 0; } IntSLLNode(int i, IntSLLNode *ptr = 0) { info = i; next = ptr; } int info; IntSLLNode *next; }; //------ class IntSLList for dealing with nodes ---------------// class IntSLList { public: IntSLList() {head = tail =0; } void AddToHead(int); void AddToTail(int); void DisplayList();

29. private: IntSLLNode *head, *tail; }; void IntSLList::AddToHead(int el) { } void IntSLList::AddToTail(int el) { } void IntSLList::DisplayList() { }

30. void main() { IntSLList myllist; myllist.AddToHead(50); myllist.AddToHead(90); myllist.AddToHead(60); myllist.DisplayList(); myllist.AddToTail(88); myllist.AddToTail(77); myllist.AddToHead(66); myllist.AddToHead(50); myllist.DisplayList(); }

31. TheAnswer# #include using namespace std; //------ class IntSLLNode for creating new node ---------------// class IntSLLNode { public: IntSLLNode() { next = 0; } IntSLLNode(int i, IntSLLNode *ptr = 0) { info = i; next = ptr; } int info; IntSLLNode *next; }; //------ class IntSLList for dealing with nodes ---------------// class IntSLList { public: IntSLList() {head = tail =0; } void AddToHead(int); void AddToTail(int); void DisplayList(); private: IntSLLNode *head, *tail; };

32. void IntSLList::AddToHead(int el) { head= new IntSLLNode (el,head); If (tail==0) Tail= head; } void IntSLList::AddToTail(int el) { if (tail !=0 ) // if list not empty { tail-> next = new IntSLLNode (el); tail=tail->next; }

33. void IntSLList::DisplayList() { IntSLLNode *current; current = head; cout << "head = " << head << "\n"; while(current != 0) {cout info << " " << current << "\n"; current=current->next;} cout << "tail = " << tail << "\n"; cout << "----------------------" << "\n";} } void main() { IntSLList myllist; myllist.AddToHead(50); myllist.AddToHead(90); myllist.AddToHead(60); myllist.DisplayList(); myllist.AddToTail(88); myllist.AddToTail(77); myllist.AddToHead(66); myllist.AddToHead(50); myllist.DisplayList(); }

34. Exercise # 2: Edit the previous program to: Add (30) to the head. Add (22) to the tail. Display all nodes.

35. #include using namespace std; //------ class IntSLLNode for creating new node ---------------// class IntSLLNode { public: IntSLLNode() { next = 0; } IntSLLNode(int i, IntSLLNode *ptr = 0) { info = i; next = ptr; } int info; IntSLLNode *next; }; //------ class IntSLList for dealing with nodes ---------------// class IntSLList { public: IntSLList() {head = tail =0; } void AddToHead(int); void AddToTail(int); void DisplayList(); private: IntSLLNode *head, *tail; };

36. void IntSLList::AddToHead(int el) { head= new IntSLLNode (el,head); if (tail==0) tail= head; } void IntSLList::AddToTail(int el) { tail-> next = new IntSLLNode (el); tail=tail->next; }

37. void IntSLList::DisplayList() {IntSLLNode *current; current = head; cout << "head = " << head << "\n"; while(current != 0) {cout info << " " << current << "\n"; current=current->next;} cout << "tail = " << tail << "\n"; cout << "----------------------" << "\n"; } void main() { IntSLList myllist; myllist.AddToHead(30); myllist.DisplayList(); myllist.AddToTail(22); myllist.DisplayList(); }

39. Evolution question Create empty linked list and then add a new node with data 50

40. Answer of Evolution question