Doubly Linked List

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Programming

• Doubly Linked List

2
Doubly Linked Lists

• In a Doubly Linked List each item points to both
  its predecessor and successor
• prev points to the predecessor
• next points to the successor

20
Head
Cur-gtnext
Cur-gtprev
Cur
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Motivation

• Doubly linked lists are useful for playing video
  and sound files with rewind and instant
  replay
• They are also useful for other linked data which
  require rewind and fast forward of the data

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Doubly Linked List Definition

• include ltiostreamgt
• using namespace std
• struct Node
• int data
• Node next
• Node prev
• typedef Node NodePtr

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Doubly Linked List Operations

• insertNode(NodePtr Head, int item)
• //add new node to ordered doubly linked list
• deleteNode(NodePtr Head, int item)
• //remove a node from doubly linked list
• searchNode(NodePtr Head, int item)
• print(NodePtr Head, int item)

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Deleting a Node

• Delete a node Cur (not at front or rear)
• (Cur-gtprev)-gtnext Cur-gtnext
• (Cur-gtnext)-gtprev Cur-gtprev
• delete Cur

Head
Cur
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Inserting a Node

• Insert a node New before Cur (not at front or
  rear)

New-gtnext Cur New-gtprev Cur-gtprev Cur-gtprev
New (New-gtprev)-gtnext New
Head
Cur
New
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Doubly Linked Lists with Dummy Head Node

• To simplify insertion and deletion by avoiding
  special cases of deletion and insertion at front
  and rear, a dummy head node is added at the head
  of the list
• The last node also points to the dummy head node
  as its successor

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Doubly Linked Lists with Dummy Head

• Non-Empty List
• Empty List

Dummy Head Node
Head
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• void createHead(NodePtr Head)
• Head new Node
• Head-gtnext Head
• Head-gtprev Head

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Deleting a Node

• Delete a node Cur at front

(Cur-gtprev)-gtnext Cur-gtnext (Cur-gtnext)-gtprev
Cur-gtprev delete Cur
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• Delete a node Cur in the middle

(Cur-gtprev)-gtnext Cur-gtnext (Cur-gtnext)-gtprev
Cur-gtprev delete Cur // same as delete front!
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• Delete a node Cur at rear

(Cur-gtprev)-gtnext Cur-gtnext (Cur-gtnext)-gtprev
Cur-gtprev delete Cur // same as delete front
and middle!
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• void deleteNode(NodePtr Head, int item)
• NodePtr Cur
• Cur searchNode(Head, item)
• if(Cur ! NULL)
• Cur-gtprev-gtnext Cur-gtnext
• Cur-gtnext-gtprev Cur-gtprev
• delete Cur

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Inserting a Node

• Insert a Node New after dummy node and before Cur

New-gtnext Cur New-gtprev Cur-gtprev Cur-gtprev
New (New-gtprev)-gtnext New
Dummy Head Node
Head
Cur
New
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• Insert a Node New in the middle and before Cur

New-gtnext Cur New-gtprev Cur-gtprev Cur-gtprev
New (New-gtprev)-gtnext New // same as insert
front!
Dummy Head Node
Cur
New
Head
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• Insert a Node New at Rear (with Cur pointing to
  dummy head)

New-gtnext Cur New-gtprev Cur-gtprev Cur-gtprev
New (New-gtprev)-gtnext New // same as insert
front!
Dummy Head Node
New
Head
Cur
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• Insert a Node New to Empty List (with Cur
  pointing to dummy head node)

New-gtnext Cur New-gtprev Cur-gtprev Cur-gtprev
New (New-gtprev)-gtnext New
Dummy Head Node
Head
New
Cur
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• void insertNode(NodePtr Head, int item)
• NodePtr New, Cur
• New new Node
• New-gtdata item
• Cur Head-gtnext
• while(Cur ! Head) //position Cur for insertion
  
• if(Cur-gtdata lt item)
• Cur Cur-gtnext
• else
• break
• New-gtnext Cur
• New-gtprev Cur-gtprev
• Cur-gtprev New
• (New-gtprev)-gtnext New

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Searching a node

• NodePtr searchNode(NodePtr Head, int item)
• NodePtr Cur Head-gtnext
• while(Cur ! Head)
• if(Cur-gtdata item)
• return Cur
• if(Cur-gtdata lt item)
• Cur Cur-gtnext
• else
• break
• return NULL

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Print the whole list

• void print(NodePtr Head)
• NodePtr CurHead-gtnext
• while(Cur ! Head)
• cout ltlt Cur-gtdata ltlt " "
• Cur Cur-gtnext
• cout ltlt endl

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• void main()
• NodePtr Head, temp
• createHead(Head)
• print(Head)
• insertNode(Head, 3)
• print(Head)
• insertNode(Head, 5)
• print(Head)
• insertNode(Head, 2)
• print(Head)
• insertNode(Head, 7)
• insertNode(Head, 1)
• insertNode(Head, 8)
• print(Head)
• deleteNode(Head, 7)
• deleteNode(Head, 0)
• print(Head)
• temp searchNode(Head, 5)

Result is 3 3 5 2 3 5 1 2 3 5 7 8 1 2 3 5
8 Data is contained in the list