Linked Lists CMSC 202 Version 402 Types of

Linked Lists CMSC 202, Version 4/02

Types of Linked Lists • • Singly-linked list Doubly-linked list Singly, circularly-linked list Doubly, circularly-linked list CMSC 202, Version 4/02 2

Singly-linked List data head pointer head node tail* *Some refer to only the last node as the tail CMSC 202, Version 4/02 3

Doubly-linked List data head pointer CMSC 202, Version 4/02 4

Singly, Circularly-linked List data head pointer CMSC 202, Version 4/02 5

Doubly, Circularly-linked List data head pointer CMSC 202, Version 4/02 6

Singly-linked List in OO other private data members* list object data object node object *May include maximum number of nodes, current number of nodes, or other items. CMSC 202, Version 4/02 7

A Look at Common Operations on a Singly-linked List • Locating an item • Inserting an item • Removing an item CMSC 202, Version 4/02 8

Locating an Item Other Private Data members 10 42 63 head next CMSC 202, Version 4/02 99 9

Locating an Item (con’t) • Design Decision: – What do we do if the item is not in the list? • Performance: – What is the best case performance? – What is the worst case performance? – What is the average performance? – How is the performance different in a sorted linked list (best, worst, average cases)? – Sorted or unsorted, would the performance be better if the list were doubly-linked? CMSC 202, Version 4/02 10

Inserting an Item Insert 17 at the head Other Private Data members 10 42 63 head next CMSC 202, Version 4/02 99 11

Inserting an Item (con’t) Insert 17 in sorted order Other Private Data members 10 42 63 head next CMSC 202, Version 4/02 99 12

Inserting an Item (con’t) In general, with a sorted list, there are three cases: - insert as first node - insert as last node - insert somewhere in between Other Private Data members 10 42 63 head next CMSC 202, Version 4/02 99 13

Inserting an Item (con’t) Design Decision: • What do we do if duplicates are not allowed? Performance: • If the list is not maintained in sorted order, it is most efficient to insert at the head. • What is the asymptotic performance of this kind of insert? – If we choose to insert at the end of the list, what is the asymptotic performance? CMSC 202, Version 4/02 14

Inserting an Item (con’t) • If the list is maintained in sorted order, we must search to find the proper place in the list, then insert. – What is the asymptotic performance of this insert? • Would performance be better if the list were doubly-linked? CMSC 202, Version 4/02 15

Removing an Item Other Private Data members 10 17 42 63 head next 99 Three cases: - remove first item - remove last item - remove an item in between CMSC 202, Version 4/02 16

Removing an Item (con’t) How does the algorithm change if we use a doubly-linked list? Other Private Data members 10 17 42 63 99 head next prev CMSC 202, Version 4/02 17

Removing an Item (con’t) Design decisions: • What do we do if the item we are asked to delete is not in the list? • What do we do if duplicates are allowed in the list? Performance: • Would performance be better if the list were doubly-linked? CMSC 202, Version 4/02 18