CSCE 210 Data Structures and Algorithms

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CSCE 210Data Structures and Algorithms

• Prof. Amr Goneid
• AUC
• Part 6. Linked Lists

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Linked Lists

• The Linked List Structure
• Some Linked List Operations
• Variations on Linked Lists

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1. The Linked List Structure

• Arrange dynamically allocated structures into a
  new structure called a linked list
• Think of a set of childrens pop beads
• Connecting beads to make a chain
• You can move things around and re-connect the
  chain
• We use pointers to create the same effect

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The Simple Linked List

• A sequence of nodes linked by pointers
• First node pointed to by head. Contains a data
  element (e) and a next pointer to next node.
• Last nodes next is NULL.
• A cursor points to the current node. It can
  advance in one way only to next node, e.g. to
  traverse whole list.

e
NULL
Last
head
First
next
cursor
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Specifying Node Structure(Example)

• Suppose each node is to contain a word from the
  dictionary, and the number of times such word
  occurs in a document.
• struct elType // specify data element
• string word int count
• struct node // specify node structure
• elType e node next
• node p, q // pointers to nodes of type node

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Specifying Node Structure

• Each of the pointers p, q can point to a struct
  of type node
• e.word (string)
• e.count (int)
• next (pointer to next node)

Struct of type node
word
count
next
String Integer Address
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Building Nodes

• Allocate storage of 2 nodes
• p new node
• q new node
• Assign data to nodes
• elType el1 , el2
• el1.word hat el1.count 2
• el2.word top el2. count 3
• p-gte el1 q-gte el2

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Building Nodes

p
hat
2
?
top
3
?
q
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Connecting Nodes A linked list of two nodes

• Suppose the address in q is stored in next
  field of node pointed to by p and NULL is stored
  in the last next field
• p-gtnext q q-gtnext NULL

p
hat
2
next
top
3
NULL
q
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2. Some Linked List Operations

• Insertion at head of list
• Inserting a node after a given node
• Insert at end of list
• Delete a head node
• Delete a non-head node

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Insertion at Head of List
Last
First
hat 2
top 3
head
2
3
elType el el.word if el.count 4 p new
node p-gt e el p-gtnext head head p
New
if 4
1
p
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Inserting after a given Node
cursor
head
top 3
hat 2
if 4
2
3
el.word the el.count 5 p new node p-gt
e el p-gt next cursor-gt next cursor-gtnext
p
p
the 5
New
1
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Insert at End of List
cursor
Last
hat 2
top 3
3
New
p new node p-gte el p-gtnext
NULL cursor-gtnext p
2
if 4
1
p
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Delete Head Node
1
cursor
head
hat 2
the 5
top 3
if 4
3
2
cursor head head head-gtnext delete cursor
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Deleting a Non-Head Node
cursor
cursor
prev
q
Successor
1
the
top
hat
3
Pre cursor points to node prev points to
predecessor node
2
node q q cursor cursor cursor-gtnext prev-gt
next cursor delete q
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Demo

• http//www.cosc.canterbury.ac.nz/people/mukundan/d
  sal/LinkListAppl.html

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3. Variations on Linked Lists

• The Circular List
• Notice that tail-gtnext head

head
tail
cursor
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Variations on Linked Lists

• The Doubly Linked List
• To advance cursor cursor-gtnext
• To back cursor cursor-gtback

next
back
cursor
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Variations on Linked Lists

• The Circular Doubly Linked List
• The 2-D List

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Learn on your own about

• Circular Linked Lists
• Doubly Linked Lists
• Multi-Lists