Linked List A group of data which is linked each other.

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1 Linked List A group of data which is linked each other

2 Linked List via Array Linked List ADT Linked List Iteration ADT Ordered List ADT Sorted List ADT Double Linked List ADT Circular Linked List ADT

3 List Representation Via Array Difficult to organize a2a2 a1a1 unusedanan A n-1 A n-2 … a3a3 0 1 2 3 n-2 n-1 n m Size n

4 a2a2 a1a1 a9a9 A8A8 A7A7 a3a3 1 2 3 4 5 6 7 8 9 10 a4a4 a5a5 a6a6 a4a4 List Using Array a2a2 a1a1 a3a3 1 2 3 4 5 6 7 8 9 Insertion a4a4 a4a4 Insert(‘new’, 4) Shift right 1 position Position to insert a2a2 a1a1 a9a9 A8A8 A7A7 a3a3 1 2 3 4 5 6 7 8 9 10 a4a4 a5a5 a6a6 ‘new’a9a9 A8A8 A7A7 a6a6 a5a5

5 a2a2 a1a1 a9a9 a8a8 a7a7 a3a3 1 2 3 4 5 6 7 8 9 10 a4a4 a5a5 a6a6 ‘new’ List Using Array Deletion delete(7) Shift left 1 position Position to delete a2a2 a1a1 a9a9 a8a8 a7a7 a3a3 1 2 3 4 5 6 7 8 9 a4a4 a5a5 ‘new’a2a2 a1a1 a9a9 a8a8 a7a7 a3a3 1 2 3 4 5 6 7 8 9 10 a4a4 a5a5 a6a6 ‘new’

6 Linked-list Insertion/deletion is slow cause it has to shift items in contiguous memory HIGH COST Items is not need to be contiguous

7 List Node a Element next class ListNode{ Object element; ListNode next; ListNode(Object obj) { element = obj; next = null; } ListNode(Object obj, ListNode node) { element = obj; next = node; }

8 List Node a1a1 a2a2 a3a3 head a4a4 null ListNode node4 = new ListNode(a4);// new ListNode(a4, null); ListNode node3 = new ListNode(a3, node4); ListNode node2 = new ListNode(a2, node3); ListNode head = new ListNode(a1, node2);

9 Linked-List Linked-List ADT a1a1 a2a2 a3a3 head a4a4 null LinkedList() addHead(obj) isEmpty() deleteHead() retrieveHead() getHead()

10 Linked-List list Linked-List LinkedList list = new LinkedList(); list.add(a4); list.add(a3);// list.insert(a3,a4); list.add(a2); // list.insert (a2,a3); list.add(a1); a1a1 a2a2 a3a3 head a4a4 LinkedList()

11 Linked-List Inserting Node a1a1 a2a2 a3a3 a4a4 head current X obj temp

12 Linked-List Inserting Node We need a help to point node before inserted node (say it ‘current’) Inserted node is named newNode a1a1 a2a2 a4a4 head current X obj newNode public void insertNext (Object obj) { ListNode newNode; if (current != null) { newNode = new ListNode(obj, current.next); current.next = newNode; } else if (zeroflag) head = new ListNode(obj,head); else {throw new ItemNotFound(“insert fails”)} }

13 Linked-List Deleting Node We need a help to point node before deleted node (say it ‘current’) Deleted node is node after current a1a1 a2a2 a4a4 head current public void deleteNext (Object obj) { current = head; while (current.element != obj && current.next != null) current = current.next; if (current.next != null) { ListNode temp = current.next;// code in C++ current.next = current.next.next; release(temp); // code in C++ } else {throw new ItemNotFound(“delete fails”)} } a3a3 X temp

14 Linked-List Linked-List Iteration ADT LinkedListItr() zeroth() retrieve() deleteNext() isLast() isInList() first() advance() insertNext(obj) Linked-ListItr current a1a1 a2a2 a3a3 head a4a4 null acces and change nodes acces and change current pointer

15 Linked-List Inserting Node in Linked List Iteration We have had current that points to a node before inserted position Node is inserted after current position Inserted node is named newNode a1a1 a2a2 a4a4 head current X obj newNode public void insertNext (Object obj) { ListNode newNode; if (isInList()) { newNode = new ListNode(obj, current.next); current.next = newNode; } else if (zeroflag) head = new ListNode(obj,head); else {throw new ItemNotFound(“insert fails”)} }

16 Linked-List Deleting Node in Linked List Iteration Deleted node is node after current a1a1 a2a2 a4a4 head current public void deleteNext () { current = head; while (current.element != obj && current.next != null) current = current.next; if (current.next != null) { ListNode temp = current.next;// code in C++ current.next = current.next.next; release(temp); // code in C++ } else {throw new ItemNotFound(“delete fails”)} } a3a3 X temp

17 Retrieve Next Element in Linked List Iteration Linked-List public int retrieveNext() { if (current.next() <>null)//if(isInList()) return current.next.element; else return null; }

18 OrderedList Ordered List ADT list OrderedList () insert (obj, index) delete(index) retrieve (index) length() Linked-List Iteration ADT

19 Ordered List Implementation Linked-List class OrderedList ( private LinkedListItr list; private int pos=0; public OrderedList() {list=new LinkedListItr ();} public int length() { int count=0; for (list.first(); list.isInList(); list.advance()) {count++;} return count; } public int retrieve(int i) { if (this.setPos(i)) return list.retrieve(); else return null; } private setPos(int i) { if (pos>i) {list.first(); pos=0;} for (int i=i-pos; list.isInList(); list.advance()) { pos++; } public advance() { if (! list.isLast()) { list.advance(); pos++; }

20 OrderedList Sorted List ADT list SortedList () insert (obj) delete(index) retrieve (index) length() Linked-List Iteration ADT