All Operation with Algorithms of Doubly linked list (Animated)

1. Doubly-Linked List

2. 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

3. prev next
Info
NODE
Node Data
 Info : the user’s data.
 Prev, Next : the address of next and
previous node in list

4. 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.

5. Create doubly linked list
NULL
7 X
X 9 X

6. Algorithm
Step 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. Insert an element at beginning
doubly linked list
We assume linked list
first last
7 9 X
X 2 X

8. 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

9. Insert an element at last of
doubly linked list
We assume linked list
first last
X 2 7 9
X 4 X

10. 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

11. Insert an element at Any place
doubly linked list
first last
X 2 7 9
4 X
We assume linked list and
Insert after 7 valued node
6
tra
t1

12. 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

13. 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

14. Delete an element at beginning
of doubly linked list
first last
X 2 7 9
4 X
We assume linked list
ffirst
X

15. 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

16. Delete an element at last of
doubly linked list
first last
X 2 7 9
4 X
We assume linked list
t
X

17. 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

18. Delete an element at any place
doubly linked list
We assume linked list and
Delete 7 valued node
first last
X 2 7 9
4 X
tra
t1
pr1

19. 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

20. 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