Why Circular? In a singly linked list, for accessing any node of the linked list, we start traversing from the first node. If we are at any node in the middle of the list, then it is not possible to access nodes that precede the given node. This problem can be solved by slightly altering the structure of a singly linked list. In a singly linked list, the next part (pointer to next node) is NULL. If we utilize this link to point to the first node, then we can reach the preceding nodes. Refer to this for more advantages of circular linked lists. The structure thus formed is a circular singly linked list and looks like this:
In this post, the implementation and insertion of a node in a Circular Linked List using a singly linked list are explained.
Implementation To implement a circular singly linked list, we take an external pointer that points to the last node of the list. If we have a pointer last pointing to the last node, then last -> next will point to the first node.
The pointer last points to node Z and last -> next points to node P.
Why have we taken a pointer that points to the last node instead of the first node? For the insertion of a node at the beginning, we need to traverse the whole list. Also, for insertion at the end, the whole list has to be traversed. If instead of start pointer, we take a pointer to the last node, then in both cases there won’t be any need to traverse the whole list. So insertion at the beginning or at the end takes constant time, irrespective of the length of the list.
Insertion A node can be added in three ways:
Insertion in an empty list
Insertion at the beginning of the list
Insertion at the end of the list
Insertion in between the nodes
Insertion in an empty List Initially, when the list is empty, the last pointer will be NULL.
After inserting node T,
After insertion, T is the last node, so the pointer last points to node T. And Node T is the first and the last node, so T points to itself. Function to insert a node into an empty list,
C++
struct Node *addToEmpty(struct Node *last, int data)
{
// This function is only for empty list
if (last != NULL)
return last;
// Creating a node dynamically.
struct Node *temp =
(struct Node*)malloc(sizeof(struct Node));
// Assigning the data.
temp -> data = data;
last = temp;
// Note : list was empty. We link single node
// to itself.
temp -> next = last;
return last;
}
Java
static Node addToEmpty(Node last, int data)
{
// This function is only for empty list
if (last != null)
return last;
// Creating a node dynamically.
Node temp = new Node();
// Assigning the data.
temp.data = data;
last = temp;
// Note : list was empty. We link single node
// to itself.
temp.next = last;
return last;
}
// This code is contributed by gauravrajput1
Python3
# This function is only for empty list
def addToEmpty(self, data):
if (self.last != None):
return self.last
# Creating the newnode temp
temp = Node(data)
self.last = temp
# Creating the link
self.last.next = self.last
return self.last
# this code is contributed by shivanisinghss2110
C#
static Node addToEmpty(Node last, int data)
{
// This function is only for empty list
if (last != null)
return last;
// Creating a node dynamically.
Node temp =
new Node();
// Assigning the data.
temp.data = data;
last = temp;
// Note : list was empty. We link single node
// to itself.
temp.next = last;
return last;
}
// This code contributed by umadevi9616
Javascript
Insertion at the beginning of the list To insert a node at the beginning of the list, follow these steps: 1. Create a node, say T. 2. Make T -> next = last -> next. 3. last -> next = T.
After insertion,
Function to insert nodes at the beginning of the list,
C++
struct Node *addBegin(struct Node *last, int data)
{
if (last == NULL)
return addToEmpty(last, data);
// Creating a node dynamically.
struct Node *temp
= (struct Node *)malloc(sizeof(struct Node));
// Assigning the data.
temp -> data = data;
// Adjusting the links.
temp -> next = last -> next;
last -> next = temp;
return last;
}
Java
static Node addBegin(Node last, int data)
{
if (last == null)
return addToEmpty(last, data);
// Creating a node dynamically
Node temp = new Node();
// Assigning the data
temp.data = data;
// Adjusting the links
temp.next = last.next;
last.next = temp;
return last;
}
// This code is contributed by rutvik_56
Python3
def addBegin(self, data):
if (self.last == None):
return self.addToEmpty(data)
temp = Node(data)
temp.next = self.last.next
self.last.next = temp
return self.last
# this code is contributed by shivanisinghss2110
C#
static Node addBegin(Node last, int data)
{
if (last == null)
return addToEmpty(last, data);
// Creating a node dynamically
Node temp = new Node();
// Assigning the data
temp.data = data;
// Adjusting the links
temp.next = last.next;
last.next = temp;
return last;
}
// This code is contributed by Pratham76
Javascript
Insertion at the end of the list To insert a node at the end of the list, follow these steps: 1. Create a node, say T. 2. Make T -> next = last -> next; 3. last -> next = T. 4. last = T.
After insertion,
Function to insert a node at the end of the List
C++
struct Node *addEnd(struct Node *last, int data)
{
if (last == NULL)
return addToEmpty(last, data);
// Creating a node dynamically.
struct Node *temp =
(struct Node *)malloc(sizeof(struct Node));
// Assigning the data.
temp -> data = data;
// Adjusting the links.
temp -> next = last -> next;
last -> next = temp;
last = temp;
return last;
}
Java
static Node addEnd(Node last, int data)
{
if (last == null)
return addToEmpty(last, data);
// Creating a node dynamically.
Node temp = new Node();
// Assigning the data.
temp.data = data;
// Adjusting the links.
temp.next = last.next;
last.next = temp;
last = temp;
return last;
}
// This code is contributed by shivanisinghss2110
Python3
def addEnd(self, data):
if (self.last == None):
return self.addToEmpty(data)
# Assigning the data.
temp = Node(data)
# Adjusting the links.
temp.next = self.last.next
self.last.next = temp
self.last = temp
return self.last
# This code is contributed by shivanisinghss2110
C#
static Node addEnd(Node last, int data)
{
if (last == null)
return addToEmpty(last, data);
// Creating a node dynamically.
Node temp = new Node();
// Assigning the data.
temp.data = data;
// Adjusting the links.
temp.next = last.next;
last.next = temp;
last = temp;
return last;
}
// This code is contributed by shivanisinghss2110
Javascript
Insertion in between the nodes To insert a node in between the two nodes, follow these steps: 1. Create a node, say T. 2. Search for the node after which T needs to be inserted, say that node is P. 3. Make T -> next = P -> next; 4. P -> next = T. Suppose 12 needs to be inserted after the node has the value 10,
After searching and insertion,
Function to insert a node at the end of the List,
C++
struct Node *addAfter(struct Node *last, int data, int item)
cout << item << " not present in the list." << endl;
return last;
}
void traverse(struct Node *last)
{
struct Node *p;
// If list is empty, return.
if (last == NULL)
{
cout << "List is empty." << endl;
return;
}
// Pointing to first Node of the list.
p = last -> next;
// Traversing the list.
do
{
cout << p -> data << " ";
p = p -> next;
}
while(p != last->next);
}
// Driven Program
int main()
{
struct Node *last = NULL;
last = addToEmpty(last, 6);
last = addBegin(last, 4);
last = addBegin(last, 2);
last = addEnd(last, 8);
last = addEnd(last, 12);
last = addAfter(last, 10, 8);
traverse(last);
return 0;
}
Java
class GFG
{
static class Node
{
int data;
Node next;
};
static Node addToEmpty(Node last, int data)
{
// This function is only for empty list
if (last != null)
return last;
// Creating a node dynamically.
Node temp = new Node();
// Assigning the data.
temp.data = data;
last = temp;
// Creating the link.
last.next = last;
return last;
}
static Node addBegin(Node last, int data)
{
if (last == null)
return addToEmpty(last, data);
Node temp = new Node();
temp.data = data;
temp.next = last.next;
last.next = temp;
return last;
}
static Node addEnd(Node last, int data)
{
if (last == null)
return addToEmpty(last, data);
Node temp = new Node();
temp.data = data;
temp.next = last.next;
last.next = temp;
last = temp;
return last;
}
static Node addAfter(Node last, int data, int item)
{
if (last == null)
return null;
Node temp, p;
p = last.next;
do
{
if (p.data == item)
{
temp = new Node();
temp.data = data;
temp.next = p.next;
p.next = temp;
if (p == last)
last = temp;
return last;
}
p = p.next;
} while(p != last.next);
System.out.println(item + " not present in the list.");
return last;
}
static void traverse(Node last)
{
Node p;
// If list is empty, return.
if (last == null)
{
System.out.println("List is empty.");
return;
}
// Pointing to first Node of the list.
p = last.next;
// Traversing the list.
do
{
System.out.print(p.data + " ");
p = p.next;
}
while(p != last.next);
}
// Driven code
public static void main(String[] args)
{
Node last = null;
last = addToEmpty(last, 6);
last = addBegin(last, 4);
last = addBegin(last, 2);
last = addEnd(last, 8);
last = addEnd(last, 12);
last = addAfter(last, 10, 8);
traverse(last);
}
}
/* This code contributed by PrinciRaj1992 */
Python3
class Node:
def __init__(self, data):
self.data = data
self.next = None
class CircularLinkedList:
def __init__(self):
self.last = None
# This function is only for empty list
def addToEmpty(self, data):
if (self.last != None):
return self.last
# Creating the newnode temp
temp = Node(data)
self.last = temp
# Creating the link
self.last.next = self.last
return self.last
def addBegin(self, data):
if (self.last == None):
return self.addToEmpty(data)
temp = Node(data)
temp.next = self.last.next
self.last.next = temp
return self.last
def addEnd(self, data):
if (self.last == None):
return self.addToEmpty(data)
temp = Node(data)
temp.next = self.last.next
self.last.next = temp
self.last = temp
return self.last
def addAfter(self, data, item):
if (self.last == None):
return None
temp = Node(data)
p = self.last.next
while p:
if (p.data == item):
temp.next = p.next
p.next = temp
if (p == self.last):
self.last = temp
return self.last
else:
return self.last
p = p.next
if (p == self.last.next):
print(item, "not present in the list")
break
def traverse(self):
if (self.last == None):
print("List is empty")
return
temp = self.last.next
while temp:
print(temp.data, end = " ")
temp = temp.next
if temp == self.last.next:
break
# Driver Code
if __name__ == '__main__':
llist = CircularLinkedList()
last = llist.addToEmpty(6)
last = llist.addBegin(4)
last = llist.addBegin(2)
last = llist.addEnd(8)
last = llist.addEnd(12)
last = llist.addAfter(10,8)
llist.traverse()
# This code is contributed by
# Aditya Singh
C#
using System;
public class GFG
{
public class Node
{
public int data;
public Node next;
};
static Node addToEmpty(Node last, int data)
{
// This function is only for empty list
if (last != null)
return last;
// Creating a node dynamically.
Node temp = new Node();
// Assigning the data.
temp.data = data;
last = temp;
// Creating the link.
last.next = last;
return last;
}
static Node addBegin(Node last, int data)
{
if (last == null)
return addToEmpty(last, data);
Node temp = new Node();
temp.data = data;
temp.next = last.next;
last.next = temp;
return last;
}
static Node addEnd(Node last, int data)
{
if (last == null)
return addToEmpty(last, data);
Node temp = new Node();
temp.data = data;
temp.next = last.next;
last.next = temp;
last = temp;
return last;
}
static Node addAfter(Node last, int data, int item)
{
if (last == null)
return null;
Node temp, p;
p = last.next;
do
{
if (p.data == item)
{
temp = new Node();
temp.data = data;
temp.next = p.next;
p.next = temp;
if (p == last)
last = temp;
return last;
}
p = p.next;
} while(p != last.next);
Console.WriteLine(item + " not present in the list.");
return last;
}
static void traverse(Node last)
{
Node p;
// If list is empty, return.
if (last == null)
{
Console.WriteLine("List is empty.");
return;
}
// Pointing to first Node of the list.
p = last.next;
// Traversing the list.
do
{
Console.Write(p.data + " ");
p = p.next;
}
while(p != last.next);
}
// Driven code
public static void Main(String[] args)
{
Node last = null;
last = addToEmpty(last, 6);
last = addBegin(last, 4);
last = addBegin(last, 2);
last = addEnd(last, 8);
last = addEnd(last, 12);
last = addAfter(last, 10, 8);
traverse(last);
}
}
// This code contributed by Rajput-Ji
Javascript
Output:
2 4 6 8 10 12
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Article Tags :
Linked List
circular linked list
Practice Tags :
Linked List
circular linked list
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C Exercises: Insert a node at the end of a circular linked list
Last update on December 20 2021 09:10:57 (UTC/GMT +8 hours)
Insertion In Circular Linked List
There are three situation for inserting element in Circular linked list. 1.Insertion at the front of Circular linked list. 2.Insertion in the middle of the Circular linked list. 3.Insertion at the end of the Circular linked list.
Circular Linked List
In this article, you will learn what circular linked list is and its types with implementation.
A circular linked list is a type of linked list in which the first and the last nodes are also connected to each other to form a circle.
There are basically two types of circular linked list:
1. Circular Singly Linked List
Here, the address of the last node consists of the address of the first node.
Circular Linked List Representation
2. Circular Doubly Linked List
Here, in addition to the last node storing the address of the first node, the first node will also store the address of the last node.
Circular Doubly Linked List Representation
Note: We will be using the singly circular linked list to represent the working of circular linked list.
