Preeja Unit1 Linked List (1)

8/11/2019 Preeja Unit1 Linked List (1)

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Preeja


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Suppose I have an array: 1,4,10,19,6 I want to insert a 7 between the 4 and the 10

What do I need to do?


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A linked list is fundamentally different way of storing collections each element stores a reference to the element after it

Arrays


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Linked Lists vs Arrays Arrays have a pre -determined fixed size easy access to any element a[i] in constant time

no space overhead Size = n x sizeof(element)Linked lists 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 need to hop through all previous elements


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Linked list List of items, called nodes

The order of the nodes is determined by the address,called the link, stored in each nodeEvery node (except the last node) contains the addressof the next node

Components of a nodeData: stores the relevant information Link: stores the address of the next node


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Head or firstHolds the address of the first node in the listThe info part of the node can be either a value of aprimitive type or a reference to an object


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Class Node Represents nodes on a list

It has two instance variablesinfo (of type int, but it can be any other type) link (of type Node)

public class Node {public int info;public Node link;

}


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Linked List: Some Properties


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Now consider the statement

current = head;


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Now consider the statement

current = current. Link;


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Traversing a Linked ListBasic operations of a linked list that require the link

to be traversed

Search the list for an itemInsert an item in the listDelete an item from the list

You cannot use head to traverse the list You would lose the nodes of the list Use another reference variable of the same type as

head: current


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Write code to print out the data stored in each nodein a linked list

current = head; while (current != null){System.out.println (current.info + ); current = current.link;}


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InsertionConsider the following linked list

You want to create a new node with info 50 and insertit after p


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The following statements create and store 50 in theinfo field of a new nodeNode newNode = new Node(); //create newNodenewNode.info = 50; //store 50 in the new node


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The following statements insert the node in the linkedlist at the required placenewNode.link = p.link;p.link = newNode;


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DeletionConsider the following linked list


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Linked Lists 20

Inserting at the Head1. Allocate a new node2. update new element

3. Have new node pointto old head

4. Update head to pointto new node


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Linked Lists 21

Inserting at the Tail1. Allocate a new node2. Insert new element3. Have new node

point to null4. Have old last node

point to new node

5. Update tail to pointto new node


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Linked Lists 22

Removing at the Head

1. Update head topoint to next nodein the list

2. Allow garbagecollector to reclaimthe former first

node


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Linked Lists 23

Removing at the Tail

Removing at the tailof a singly linked listis not efficient!There is no constant-time way to updatethe tail to point to the

previous node


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Write code to set the data in the 5th node to be 10current = head;cnt = 0; while (cnt < 4 && current != null) {current = current.link;}

if (current != null) {current.info = 10;}

Preeja Unit1 Linked List (1)

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