DLL_Vs_CLL

What is Circular Linked List ? What are Advantages and Disadvantages of Circular Linked List

In it the last node does not contain NULL pointer. Instead the last node contains a pointer that has the address of first node and thus points back to the first node. 

It is shown below: 



Advantages: 

1. If we are at a node, then we can go to any node. But in linear linked list it is not possible to go to previous node.
2. It saves time when we have to go to the first node from the last node. It can be done in single step because there is no need to traverse the in between nodes. But in double linked list, we will have to go through in between nodes. 

Disadvantages: 

1. It is not easy to reverse the linked list.
2. If proper care is not taken, then the problem of infinite loop can occur.
3. If we at a node and go back to the previous node, then we can not do it in single step. Instead we have to complete the entire circle by going through the in between nodes and then we will reach the required node. 

Advantages of Doubly linked list over singly linked list
1) A doubly linked list can be travel across in both forward and backward direction.
2) For delete operation a pointer to previous node is needed that is difficult in singly linked list so we need to traverse the list but in doubly linked list the previous node can be found easily using previous pointer.

Disadvantages of Doubly linked list over singly linked list
1) In doubly linked list extra space is required for previous pointer.

2) In all operations like insertion and deletion, an extra pointer (previous pointer) has to be maintained.

Circular Linked List

In Circular linked list all nodes are connected in such way that they form a circle and no NULL at the end of the list like a circle.

Advantages of Circular Linked Lists:
1) In this linked list any node can be a starting point. And to traverse list, we can start at any point and stop when the first node is visited again.

2) Unlike doubly linked list, in this linked list we don’t need to focus on two pointers for next and previous. So it is useful implementing a queue.

3) It is also useful for repeating list. For example operating system, so that when it reaches the end of the list of all application it can go to the front of the list

4) Circular DLL are used to implement advanced data structures like Fibonacci Heap.

Singly, Doubly & Circular Linked List

 

This is a basic type of Linked List.

	Singly	Doubly	Circular
Concept	One way direction	Two way direction	One way direction in a circle
Has head	Yes	Yes	No-because tail will refer to first node
Has tail	Yes	Yes	Yes
No of Node	1-next node	2-next node & previous node	1-next node
insert()	O(n)	O(1)	O(n)
delete()	O(n)	O(1)	O(1)
Benefit	require small space for each element	allow to traverse the list in both directions	execute to the end can be quickly