CS 307 Fundamentals of Computer Science 1 Linked Lists many slides taken from Mike Scott, UT Austin.

CS 307 Fundamentals of Computer Science

1

Linked Lists

many slides taken from Mike Scott, UT Austin


2

Recursive Data Structures Linked Lists are dynamic data structures

– They grow and shrink one element at a time, normally without some of the inefficiencies of arrays

Big O of Array Manipulations– Access the kth element– Add or delete an element in the middle of the array while maintaining

relative order– adding element at the end of array? space avail? no space avail? – add element at beginning of an array

If accesses are all at beginning or end of list, a linked structure offers improvements

Linked Lists could be used as the underlying storage container for higher level ADTs (stack, queue)


3

Nodes and Lists A different way of implementing a list Each element of a Linked List is a separate

Node object. Each Node tracks a single piece of data plus

a reference (pointer) to the next Create a new Node every time we add

something to the List Remove nodes when item removed from list

and allow garbage collector to reclaim that memory


4

Elements of Linked Listspublic class Node{ private Object myData;

private Node myNext;

public Node(){ myData = null; myNext = null; }

public Node(Object data, Node next){ myData = data; myNext = next; }

public Object getData(){ return myData; }

public Node getNext(){ return myNext; }

public void setData(Object data){ myData = data; }

public void setNext(Node next){ myNext = next; }

}


5

One Implementation of a Linked List The Nodes shown on the previous slide are

singly linked– a node refers only to the next node in the

structure– it is also possible to have doubly linked nodes. – The node has a reference to the next node in the

structure and the previous node in the structure as well

How is the end of the list indicated– myNext = null for last node– a separate dummy node class / object


6

A Simple List Interfacepublic interface IList{

void add(Object item);

void add(Object item, int pos);

Object set(Object item, int pos);

void add(List other);

Object get(int pos);

Object remove(int pos);

int size();}


7

A Linked List Implementationpublic class LinkedList implements Ilist{ private Node myHead;

private Node myTail;private int iMySize;

public LinkedList(){ myHead = null;

myTail = null;iMySize = 0;

}}LinkedList list = new LinkedList();

LinkedList

myHead iMySize

myTail

null

null

0


8

Add Element - List Empty (Before)

myHead myTail iMySize

null null 0

Object

item


9

Add Element - List Empty (After)


1

ObjectNode

myData myNext

null


10

Add Element - List Not Empty (Before)

1

Object

Node

myData myNext

null


Objectitem


11

Add Element - List Not Empty (After)

2

Object

Node

myData myNext


Object

Node

myData myNext

null


12

Code for default add public void add(Object item)


13

Code for arbitrary add public void add(Object item, int pos)


14

Code for get public Object get(int pos)


15

Code for remove public Object remove(int pos)


16

Why Linked List Are any operations with a Linked List faster

than the version from ArrayList?

What about this: public void addFront(Object item)

Big O? Array version Big O? Fast performance for removeFront as well?


17

Remove Back Method public Object removeBack()

Big O?


18

Other Possible Features of Linked Lists

Doubly Linked

Circular Dummy Nodes for first and last node in list

public class DLNode{ private Object myData;

private DLNode myNext;private DLNode myPrevious;

}


19

Default add for Doubly Linked List public void add(Object item)


20

Code for arbitrary add - Doubly Linked List

public void remove(Object item, int pos)


21

Code for removeDoubly Linked List

public Object remove(int pos)

CS 307 Fundamentals of Computer Science 1 Linked Lists many slides taken from Mike Scott, UT Austin.

Documents

element list

public object getint

public object getdata

public node getnext

separate node object

queue slide

memory slide

list public class dlnode