Post on 02-Jul-2015
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Doubly-Linked List
Doubly Linked List
In doubly linked list each node contains two points.
which points has a reference to both the next point
and pervious point of node in list.
A doubly linked list is a two-way list because one
can move in either from left to right or from right to
left
Info
prev next
NODE
Node Data
Info : the user’s data.
Prev, Next : the address of next and
previous node in list
Operations on a Doubly linked list
o Create list.
o Insert element at beginning in list.
o Insert element at end in list.
o Insert element at any place in list.
o Delete element from the beginning of list.
o Delete element from the end of list.
o Delete element from any place from list.
Create doubly linked list
NULL
last
7 X
node
9X X
AlgorithmStep 1: [initially list is empty]
First = NULL
last = NULL
Step 2: [allocate space to newly created node]
new1= create new node
Step 3: [assign value to information part of node]
info[new1]= Value
Step 4: [assign NULL to the address part for the next]
next[new1]= NULL
Step 5: [check for list is empty]
if first =NULL then
first = new1
last = new1
prev[new1]= NULL
else
next[last]= new1
prev[new1]=last
last=new1
end if
Step 6: exit
7 X9
lastfirst
We assume linked list
2X X
Insert an element at beginning
doubly linked list
Algorithm
Step 1: [allocate space to newly created node]
new1= create new node
Step 2: [check for free space]
if new1=NULL then
Write “Memory full”
Step 3: [check for list is empty]
if first=NULL then
Write “list is empty”
return
Step 4: [assign value to information part of node]
info[new1]= Value
Step 5: [store the node at first]
next[new1]= first
prev[new1]= NULL
prev[first]= new1
first=new1
Step 6: exit
X 2 7 9
lastfirst
We assume linked list
4 XX
Insert an element at last of
doubly linked list
Algorithm
Step 1: [check for list is empty]
if first=NULL then
Write “list is empty”
return
Step 2: [allocate space to newly created node]
new1= create new node
Step 3: [assign value to information part to node]
info[new1]= Value
Step 4: [store the node at last]
next[new1]= NULL
next[last]= new1
prev[new1]= last
last=new1
Step 5: exit
X 2 7 9
lastfirst
X4
We assume linked list and
Insert after 7 valued node
6
tra
t1
Insert an element at Any place
doubly linked list
Algorithm
Step 1: [check for list is empty]
if first=NULL then
Write “list is empty”
return
Step 2: [allocate space to newly created node]
new1= create new node
Step 3: [read values of information part of new node]
info[new1]=value
Step 4: [initialization]
tra=first
Step 5: [perform insertion operation]
repeat through step 7 while tra != NULL
Step 6: if info[tra] =no then
if tra=last then
next[tra]=new1
next[new1]=NULL
prev[new1]=tra
last=new1
else
t1=next[tra]
next[tra]=new1
next[new1]=t1
prev[t1]=new1
prev[new1]=tra
Step 7: [increment temp value]
tra=next[tra]
Step 8: exit
X 2 7 9
lastfirst
X4
We assume linked list
ffirst
X
Delete an element at beginning
of doubly linked list
Algorithm
Step 1: [check for list is empty]
if first=NULL then
Write “list is empty”
return
Step 2: [perform deletion opration]
if first=last then
first=NULL
last=NULL
free(first)
else
ffirst=next[first]
free(first)
first=ffirst
prev[first]=NULL
end if
Step 3: exit
X 2 7 9
lastfirst
X4
We assume linked list
t
X
Delete an element at last of
doubly linked list
Algorithm
Step 1: [check for list is empty]
if first=NULL then
Write “list is empty”
return
Step 2: [perform deletion opration]
if first=last then
first=NULL
last=NULL
free(first)
else
t=prev[last]
free(last)
last=t
next[last]=NULL
Step 3: exit
Delete an element at any place
doubly linked list
We assume linked list and
Delete 7 valued node
X 2 7 9
lastfirst
X4
tra
t1
pr1
Algorithm eny delete
Step 1: [check for list is empty]
if first=NULL then
Write “list is empty”
return
Step 2: [perform deletion opration]
if first=last then
first=NULL
last=NULL
free(first)
Step 3: [initialization]
tra=first
Step 4: [perform insertion operation]
repeat through step 7 while tra != NULL
Step 5: IF info[tra]=number then
if tra=first then
ffirst=next[first]
free(first)
first=ffirst
else if tra=first then
free(last)
last=pr1
next[last]=NULL
else
t1=next[tra]
next[pr1]=t1
prev[t1]=pr1
free(tra)
last=t1
Step 6: [Assign previous value of tra to prev]
pr1=tra
Step 7: [increment temp value]
tra=next[tra]
Step 8: exit