- 1. LINK LIST SHEETAL WAGHMARE M.TECH (Computer Science & Data Processing) IIT KHARAGPUR EMAIL-ID: shitu2iitkgp@gmail.com sheetalw3@gmail.com
- 2. Instruction To Use This Presentation Dear user I have kept some animated/executable/video files so it will be easy for you to understand but that wont be run/play in slideshow To see/run that files you have to exit from slideshow then click on the icon and also install KM Player For example: click on the below icons one by one( one is executable file and other is video) you will be able to see the animation SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 3. CONTENTS SINGLY LINKLIST (INSERTION,DELETION,SORT,SEARCH) STACK(PUSH,POP) QUEUE(ADD,REMOVE) CIRCULAR LINKLIST DOUBLE ENDED QUEUE CIRCULAR QUEUE PRIORITY QUEUE DOUBLY LINKLIST(INSERTION,DELETION,SORT,SEARCH) SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 4. What’s wrong with Array and Why lists? Disadvantages of arrays as storage data structures: slow searching in unordered array slow insertion in ordered array Fixed size Linked lists solve some of these problems SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 5. List Implementation using Linked Lists Linked list Linear collection of self-referential class objects, called nodes Connected by pointer links Accessed via a pointer to the first node of the list Link pointer in the last node is set to null to mark the list’s end Use a linked list instead of an array when You have an unpredictable number of data elements You want to insert and delete quickly. SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 6. Linked Lists A B C Head 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 node The last node points to NULL A SHEETAL WAGHMARE FROM IIT data pointer KHARAGPUR
- 7. Part II: Linked Lists As an abstract data type, a list is a finite sequence (possibly empty) of elements with basic operations that vary from one application to another. Basic operations commonly include: Construction: Allocate and initialize a list object (usually empty) Empty: Check if list is empty Insert: Add an item to the list at any point Delete: Remove an item from the list at any point Traverse: Go through the list or a part of it, accessing and processing theWAGHMARE in the order they are stored SHEETAL elements FROM IIT KHARAGPUR
- 8. Linked Representation Data structure for a linked list: first Node •Data •Link (pointer): used to store the address of the next node. SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 9. Anatomy of a linked list A linked list consists of: A sequence of nodes myList a b c d Each node contains a value and a link (pointer or reference) to some other node The last node contains a null link The list may (or may not) have a header SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 10. More terminology A node’s successor is the next node in the sequence The last node has no successor A node’s predecessor is the previous node in the sequence The first node has no predecessor A list’s length is the number of elements in it A list may be empty (contain no elements) SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 11. Linked Lists Types of linked lists: Singly linked list Begins with a pointer to the first node Terminates with a null pointer Only traversed in one direction Circular, singly linked Pointer in the last node points back to the first node Doubly linked list Two “start pointers” – first element and last element Each node has a forward pointer and a backward pointer Allows traversals both forwards and backwards Circular, doubly linked list Forward pointer of the last node points to the first node and backward pointer of the first node points to the last node SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 12. Declarations First you must declare a data structure that will be used for the nodes. For example, the following struct could be used to create a list where each node holds a float: SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 13. Conventions of Linked List There are several conventions for the link to indicate the end of the list. 1. A null link that points to no node (0 or NULL) 2. A dummy node that contains no item 3. A reference back to the first node, making it a circular list. SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 14. Convention of the linked list A special list is maintained which consists of unused memory cells. This list, which has its own pointer, is called the list of available space or the free storage list or the free pool. The operating system of a computer may periodically collect all the deleted space onto the free storage list. Any technique which does this collection is called garbage collection. SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 15. Conventions Sometimes new data are to be inserted into the data structure but there is no available space, i.e. the free storage list is empty. This situation is usually called overflow. means when AVAIL = NULL and there is an insertion. The term underflow refers to the situation where one wants to delete data from a data structure that is empty. The programmer may handle underflow by printing the message UNDERFLOW. means If START = NULL, SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 16. Inserting to the Front head 93 head 48 17 142 There is no work to find the correct location Empty or not, head will point to the right location SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 17. Insert first position INFIRST(INFO,START,AVAIL,ITEM) 1. [OVERFLOW] if AVAIL=NULL then write:OVERFLOW and exit. 2. [remove first node from AVAIL list] set NEW=AVAIL and AVAIL=LINK[AVAIL]. 3. Set INFO[NEW]=ITEM [copies new data into new node] 4. Set LINK[NEW]=START [new node now points to original first node] 5. Set START=NEW [changes START so it points to the new node] 6. Exit SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 18. Inserting to the Middle head 17 48 142 93 // 142 // Used when order is important Go to the node that should follow the one to add Recursion or iteration SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 19. Algorithm INSLOC[INFO,LINK,START,AVAIL,LOC,ITEM] 1. [OVERFLOW] if AVAIL=NULL then write OVERFLOW and exit. 2. [remove first node from AVAIL list] set NEW:=AVAIL and AVAIL:=LINK[AVAIL] 3. Set INFO[NEW]:=ITEM[copies new data into new node] 4. If LOC=NULL then [insert as a first node ] set LINK[NEW]:=START and START:=NEW Else [insert after node with location Loc] set LINK[NEW]:=LINK[LOC] and LINK[LOC]:=NEW [end of if structure] 5. Exit after.exe SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 20. Inserting to the End head 48 17 142 //93 // Find the end of the list (when at NIL) Recursion or iteration SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 21. Inserting to End of a Linked List Recursively traverse the list until at end Then: Create new node at current Fill in data Terminate the new node’s next pointer to point to NIL SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 22. Inserting to End of a Linked List 1. allocate memory for the new node. 2. Assign value to the data of the new node. 3. if START is NULL then(if the list is empty) a. Make START point to the NEW node. b. make LAST point to the new node c. go to step 6. 4. Make the next field of LAST point to the New node 5. Mark the new node as LAST. 6. Make the next field of the new node point to NULL. SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 23. Inserting to End of a Linked List INLAST(INFO,START,AVAIL,ITEM) 1. [OVERFLOW] if AVAIL=NULL then write:OVERFLOW and exit. 2, [remove first node from AVAIL list] set NEW=AVAIL and AVAIL=LINK[AVAIL]. 3. Set INFO[NEW]=ITEM [copies new data into new node] 4. If START=NULL Set START=NEW and LOC=START 5. Repeat step 6 untill LINK[LOC] != NULL 6. Set LOC=LINK[LOC] 7. Set LINK[LOC]=NEW 8. Exit SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 24. Inserting at the End of a Linked List head 48 17 142 53 current Rnew_data 53 current Rnew_data 53 current Rnew_data 53 current Rnew_data 53 SHEETAL WAGHMARE FROM IIT end.exe KHARAGPUR
- 25. Find the desired element FINDB(INFO,LINK,START,ITEM,LOC,LOCP] This function finds the location LOC of the first node N which contains ITEM and the location LOCP of the node preceding N. if ITEM does not appear in the list, then the function set LOC=NULL and it item appears in the first node then it sets LOCP=NULL] 1.[list empty?] if START=NULL then set LOC=NULL and LOCP=NULL and return. [end of if structure] 2. [ITEM in first node?] if INFO[START]==ITEM then Set LOC=START and LCOP=NULL and return. [end of if structure] 3 . Set SAVE=START and PTR=LINK[START] [intializes pointers] 4. Repeat step 5 and 6 while PTR != NULL 5. Contd……. SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 26. Contd…. 5. if INFO[PTR]=ITEM then Set LOC= PTR and LOCP=SAVE and return [end of IF structure] 6. set SAVE=PTR and PTR=LINK[PTR] [ updates pointers] [end of step 4 loop] 7. set LOC=NULL. [search unsuccessful] 8. return . SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 27. Delete DELETE(INFO,LINK,START,AVAIL,ITEM) This algorithm deletes from a linked list the first node N which contains the given ITEM of information 1.[use function FINDB] call FINDB 2. if LOC=NULL then write ITEM not in list and exit 3. [delete node] if LOCP=NULL then set START=LINK[START] [delete first node] Else set LINK[ LOCP]=LINK[LOC] [end of if structure] 4.[return deleted node to the AVAIL list] set LINK[LOC]=AVAIL and AVAIL=LOC Exit deletion.exe SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 28. Sorting SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 29. Singly Linked Lists and Arrays Singly linked list Array Elements are stored in linear Elements are stored in linear order, accessible with links. order, accessible with an index. Do not have a fixed size. Have a fixed size. Cannot access the previous Can access the previous element directly. element easily. No binary search. Binary search. SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 30. ARRAY IMPLEMENTATION OF STACK PUSH:- 1.if(top==max-1) 1.print(stack overflow) 2.else 1.top=top+1 2.stack arr[top]=pushed item 3.endif end algorithm POP:- 1.if (top==-1) 1.print(stack underflow) 2.else 1.print(popped element is stack arr[top]) 2.top=top-1 3.end if end algorithm SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 31. QUEUE IMPLEMENTATION Procedure Q INSERT (Q, FRONT, REAR,MAX,Y) 1.[Overflow ?] IF REAR>=N THEN WRITE ("OVERFLOW") RETURN 2.REAR<-REAR+1 3.Q[REAR]<-Y 4.IF FRONT=0 THEN FRONT<-1 RETURN ENQUEUE:- if(rear==(MAX-1)) print (queue overflow) elseif (front==-1) front=0 rear=rear+1 queue_arr[rear]=added_item endif SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 32. DEQUEUE if(front==-1 OR front>rear) print(queue underflow) else print(element deleted from queue,queue_arr[front]) front=front+1 end if end algorithm Procedure Q DELETE (Q,FRONT, REAR) 1.UNDERFLOW IF FRONT=0 THEN WRITE ("UNDERFLOW") RETURN 2.Y<-Q[FRONT] 3.IF FRONT=REAR THEN FRONT<-REAR<-0 ELSE REAR<-REAR+1 4.RETURN Y SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 33. PRIORITY QUEUE priority queue.swf SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 34. Circular Link list SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 35. 10 Insert into an empty list New Rear •Insert into Head of circular link list 10 20 40 55 70 New Cur Prev Rear New->next = Cur; Prev->next = New; SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 36. Insert to middle of a Circular Linked List between Pre and Cur New->next = Cur; Prev->next = New; 10 20 55 70 40 Prev Cur Rear SHEETAL WAGHMARE FROM IIT KHARAGPUR New
- 37. CIRCULAR QUEUE circular queue.swf Procedure CQINSERT(FRONT, Procedure CQDELETE REAR, Q , N ,Y) (FRONT, REAR, Q) 1.IF R=N 1.[Underflow?] THEN R<-1 IF FRONT =0 ELSE R<-R+1 WRITE UNDERFLOW 2.[Overflow?] 2.Y<-Q[REAR] IF R=F 3.IF FRONT=REAR THEN WRITE ("OVERFLOW") THEN FRONT<-REAR<-0 RETURN RETURN Y 3.Q[R]<-Y 4.IF FRONT= N 4. THEN F<-1 IF FRONT=0 ELSE F<-F+1 FRONT<-1 RETURN Y SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 38. Doubly Linklist Traversing the list Traversal of a doubly linked list can be in either direction. In fact, the direction of traversal can change many times SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 39. Forward: node := list.firstNode while node ≠ null <do something with node.data> //print the data node := node.next Backward: node := list.lastNode while node ≠ null <do something with node.data> // print data node := node.prev SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 40. Inserting into Doubly Linklist Inserting a node These symmetric functions insert a node either after or before a given node, with the diagram demonstrating after: SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 41. Insert After function insertAfter(List list, Node node, Node newNode) newNode.prev := node newNode.next := node.next if node.next == null list.lastNode := newNode else node.next.prev := newNode node.next := newNode SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 42. Insert Before function insertBefore(List list, Node node, Node newNode) newNode.prev := node.prev newNode.next := node if node.prev == null list.firstNode := newNode else node.prev.next := newNode node.prev := newNode SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 43. Insert at the Beginning function insertBeginning(List list, Node newNode) if list.firstNode == null list.firstNode := newNode list.lastNode := newNode newNode.prev := null newNode.next := null else insertBefore(list, list.firstNode, newNode) SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 44. Insert at the End function insertEnd(List list, Node newNode) if list.lastNode == null insertBeginning(list, newNode) else insertAfter(list, list.lastNode, newNode) SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 45. Deletion Deleting a node Deletion of a node is easier than insertion, but requires special handling if the node to be removed is the firstNode or lastNode: function remove(List list, Node node) if node.prev == null list.firstNode := node.next else node.prev.next := node.next if node.next == null list.lastNode := node.prev else node.next.prev := node.prev destroy node SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 46. Multi-lists Multi-lists are essentially the technique of embedding multiple lists into a single data structure. A multi-list has more than one next pointer, like a doubly linked list, but the pointers create separate lists. SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 47. Multi-lists head SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 48. Multi-lists head SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 49. Multi-lists (Not Required) head head SHEETAL WAGHMARE FROM IIT KHARAGPUR
- 50. EXAMPLE SHEETAL WAGHMARE FROM IIT KHARAGPUR