Tutorial 2: Linked Lists

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1 Tutorial 2: Linked Lists

2 ? 2

3 Agenda Introduction of Linked List Arrays Vs Linked Lists Types of Linked Lists Singly Linked List Doubly Linked List Circular Linked List Operations Insertion Deletion 3

4 Data Structures where objects will be arranged linearly Array: Linear order determined by indices Linked List: Order determined by pointer of each object Linked list provides simple & flexible representation for dynamic sets supporting various operations Head Null 4

5 Array Vs Linked List Array Pre-determined fixed size Easy access to any element a[i] in constant time No space overhead Linked List Size = N x sizeof (element) No fixed size; grow one element at a time 5

6 Linked List No fixed size; grow one element at a time Space overhead Each element must store an additional reference Size = n x sizeof (element) + n x sizeof(reference) No easy access to i th element wrt the head of the list 6

7 Inserting an element at the head of SLL Head Null Newest 5 Newest Null

8 Algorithm O(1) addfirst(e) newest = Node(e) newest.next = head head = newest size = size+1 8

9 Inserting an element at the tail of SLL Head Null Newest 5 Head Null

10 Algorithm O(1) addlast(e) newest = Node(e) newest.next = null tail.next = newest tail = newest size = size+1 10

11 Remove an element from a SLL Head Null Null Head

12 Algorithm O(1) removefirst() If (head == null) List is empty else, head = head.next size = size-1 12

13 Implementing SLL & DLL LinkedList extends AbstractSequentialList & implements List interface which extends Collection 13

14 size(): returns no. of elements isempty(): returns true or false first(): returns the first element in the list last(): returns the last element in the list addfirst(e): adds new element to front of the list addlast(e): adds new element to end of the list removefirst(): removes & returns first element 14

15 Doubly Linked List SLL and Asymmetry In SLL, difficult to delete a tail & any arbitrary node, Why? To provide greater symmetry: DLL O(1) time operations (insertion, deletion at anywhere) Previous & Next Pointer 15

16 Header & Trailer Sentinels To carry out efficient operations nearby boundaries of DLL They won t store elements of primary sequence To simplify the logic of our operations Header & Trailer nodes never change 16

18 Insert new node at beginning? Insert new node at middle? Insert new node at end? 18

19 Implementing SLL & DLL LinkedList extends AbstractSequentialList & implements List interface which extends Collection 19

20 size(): returns no. of elements isempty(): returns true or false first(): returns the first element in the list last(): returns the last element in the list addfirst(e): adds new element to front of the list addlast(e): adds new element to end of the list removefirst(): removes & returns first element 20

21 Searching a DLL LIST-SEARCH(L,k) 1. X=L.head 2. While X!=NULL & X.key!=k 3. X=X.next 4. Return X O(n) 21

22 Inserting into a DLL LIST-INSERT(L,X) 1. X.next=L.head 2. If L.head.next!=NULL 3. L.head.prev=X 4. L.head=X 5. X.prev=NULL O(1) 22

23 Deleting from a DLL O(1) LIST-DELETE(L,X) 1. If X.prev!=NULL 2. X.prev.next=X.next 3. If X.next!=Null 4. X.next.prev=X.prev 23

24 Next Tutorial... Demo & Programming Exercises 24

25 Assignments Implement Singly Circular & Doubly Circular linked list using similar techniques. How to reverse any linked list? Discuss various methods with pseudocode & write a program in JAVA using a recursive technique, asking any 10 random integers from user. Deadline: 29 March 2018, 11:59 NPT info@prakashgautam.com.np 25

26 ? Thank You 26

csci 210: Data Structures Linked lists

csci 210: Data Structures Linked lists Summary Today linked lists single-linked lists double-linked lists circular lists READING: GT textbook chapter 3.2. 3.3. 3.4 Arrays vs. Linked Lists We ve seen arrays: