Linked Lists 1© 2004 Goodrich, Tamassia

Linked Lists

Linked Lists 2© 2004 Goodrich, Tamassia

Singly Linked List (§ 4.4.1)A singly linked list is aconcrete data structureconsisting of a sequenceof nodesEach node stores element link to the next node

next

elem node

A B C D

∅

Linked Lists 3© 2004 Goodrich, Tamassia

Linked List node in Javapublic class ListNode {

Object elem;

ListNode next;

public ListNode (ListNode next, Object elem)

{this.next = next; this.elem = elem; }public Object getElem() {return elem; }

public void setElem(Object elem) {this.elem = elem; }

public ListNode getNext() {return next; }

public void setNext(ListNode next) {this.next = next; }

}

Linked Lists 4© 2004 Goodrich, Tamassia

Inserting at the Head1. Allocate a new

node2. Insert new element3. Have new node

point to old head4. Update head to

point to new node

Linked Lists 5© 2004 Goodrich, Tamassia

Removing at the Head

1. Update head topoint to next nodein the list

2. Allow garbagecollector to reclaimthe former firstnode

Linked Lists 6© 2004 Goodrich, Tamassia

Stack with a Singly Linked ListWe can implement a stack with a singly linked listThe top element is stored at the first node of the listThe space used is O(n) and each operation of the Stack ADTtakes O(1) time

∅t

nodes

elements

Linked Lists 7© 2004 Goodrich, Tamassia

Inserting at the Tail1. Allocate a new

node2. Insert new element3. Have new node

point to null4. Have old last node

point to new node5. Update tail to point

to new node

Linked Lists 8© 2004 Goodrich, Tamassia

Queue with a Singly Linked ListWe can implement a queue with a singly linked list The front element is stored at the first node The rear element is stored at the last node

The space used is O(n) and each operation of the Queue ADTtakes O(1) time

f

r

∅

nodes

elements

Linked Lists 9© 2004 Goodrich, Tamassia

Removing at the Tail

Removing at the tailof a singly linked listis not efficient!There is noconstant-time wayto update the tail topoint to the previousnode

Linked Lists 10© 2004 Goodrich, Tamassia

Doubly Linked ListA doubly linked list is a more complex type oflist that allows insertion in the middleNodes store:

element (sometimes combined into the nodeinstead of a reference)

link to the previous node link to the next node

Special trailer and header nodes

prev next

elem

trailerheader nodes/positions

elements

node

Linked Lists 11© 2004 Goodrich, Tamassia

InsertionWe visualize operation insertAfter(p, X), which returns position q

A B X C

A B C

p

A B C

p

X

q

p q

Linked Lists 12© 2004 Goodrich, Tamassia

DeletionWe visualize remove(p), where p = last()

A B C D

p

A B C

D

p

A B C