Lecture4
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This document discusses different types of linked lists including doubly linked lists, circular linked lists, and doubly circular linked lists. It provides details on the structure of each node in a doubly linked list and how elements are added and deleted. Circular linked lists are introduced as linked lists where the last node's next pointer points to the head node, forming a ring structure. Doubly circular linked lists combine the features of doubly linked lists and circular linked lists. The Josephus problem is presented as an example that can be solved using a circular linked list to model people sitting in a circle. Students are assigned to implement the Josephus problem using a linked list data structure with parameters M and N specified at runtime.
Lecture4
- 1. Lecture # 4Lecture # 4
- 2. Doubly Link ListDoubly Link List
- 3. In aIn a DoublyDoubly linked listlinked list, each, each itemitem is allocated spaceis allocated space as it is added to the list. Aas it is added to the list. A linklink is kept with eachis kept with each item to theitem to the next itemnext item andand previous itemprevious item in the list.in the list. Each node of the list hasEach node of the list has threethree elements:elements: TheThe itemitem being stored in the listbeing stored in the list A pointer to theA pointer to the nextnext item in the listitem in the list A pointer to theA pointer to the previousprevious item in the listitem in the list The last node in the list contains aThe last node in the list contains a NULLNULL pointerpointer (next)(next) to indicate that it is theto indicate that it is the endend oror tailtail of the listof the list and first node containsand first node contains NULLNULL pointer forpointer for previousprevious pointer to indicate that it ispointer to indicate that it is headhead of the Link List.of the Link List.
- 4. Figure showingFigure showing Doubly Link ListDoubly Link List …..….. BA EC headhead D NULLNULL NULNUL LL Structure corresponding to above will beStructure corresponding to above will be struct nodestruct node {{ char info;char info; node *next;node *next; node *previous;node *previous; };};
- 5. Adding element - Doubly-Linked ListAdding element - Doubly-Linked List
- 6. Deletion - Doubly-Linked ListDeletion - Doubly-Linked List How ….How …. Think yourselfThink yourself Discussion from Implementation (code)Discussion from Implementation (code) point of view.point of view.
- 7. Ring data structure can be regarded asRing data structure can be regarded as circular Link Listcircular Link List.. In Link List, instead of making last node’sIn Link List, instead of making last node’s next pointer to NULL, we can assign ornext pointer to NULL, we can assign or point it to head node so that it sounds aspoint it to head node so that it sounds as ring data structure as follows.ring data structure as follows. Circular Link List (Ring)Circular Link List (Ring)
- 8. Figure showingFigure showing RingRing…..….. BA EC headhead D OROR B A E C headhead D
- 9. Josephus ProblemJosephus Problem A case where circularly linked list is handy toA case where circularly linked list is handy to provide the solution of theprovide the solution of the Josephus ProblemJosephus Problem.. Consider there areConsider there are 1010 persons. They would like topersons. They would like to choose achoose a leaderleader.. The way they decide is thatThe way they decide is that all 10 sit in a circleall 10 sit in a circle.. They start a count with personThey start a count with person 11 and go inand go in clockwise direction and skipclockwise direction and skip 3.3. PersonPerson 44 reachedreached is eliminated.is eliminated. The count starts with the fifth and the next personThe count starts with the fifth and the next person to go is the fourth in count.to go is the fourth in count. Eventually, a single person remains.Eventually, a single person remains.
- 20. Doubly RingDoubly Ring data structure can be regarded asdata structure can be regarded as Circular Doubly Link ListCircular Doubly Link List.. InIn Circular Doubly Link ListCircular Doubly Link List, instead of making last, instead of making last node’snode’s nextnext pointer to NULL, We assign or point itpointer to NULL, We assign or point it toto headhead node. Similarly,node. Similarly, firstfirst (head) node’s(head) node’s previousprevious pointer is pointed to last node in list . sopointer is pointed to last node in list . so that it sounds asthat it sounds as Doubly RingDoubly Ring data structure.data structure. Doubly RingDoubly Ring
- 21. Figure showingFigure showing DoublyDoubly RingRing…..….. BA EC headhead D OROR B A E C headhead D
- 22. Assignment # 3Assignment # 3 Implement aImplement a Josephus ProblemJosephus Problem discusseddiscussed above with following conditions.above with following conditions. Decide value ofDecide value of MM andand NN at run time.at run time. AssignAssign numbersnumbers to every node.to every node. Initiate the problem from node numberInitiate the problem from node number 11.. Submission Due DateSubmission Due Date:: Next week, same dayNext week, same day (In Office Hours)(In Office Hours)