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Data Structure

Insertion in circular linked list: Beginning ,End and at any given position

Updated on September 20, 2025
  • Insertion at Beginning: A new node is created, its next pointer is set to the current head, and the last node’s next pointer is updated to point to this new node. Finally, the head pointer is moved to the new node.
  • Insertion at End: A new node is created, its next pointer is set to the head, and the current last node’s next pointer is updated to this new node, making it the new last node in the list.
  • Insertion at a Given Position: Insertion at any position in a circular linked list involves traversing to the node before the desired position and linking a new node between the previous and next nodes. This ensures the circular structure of the list is maintained.

In both cases, the circular property is maintained because the last node always points back to the head.

Insert a node in Beginning of circular linked list

Algorithm

Step 1: Start.
Step 2: Create a new node newNode and assign data to it.
Step 3: If the list is empty (head == NULL):
    a. Set head = newNode.
    b. Point newNode->next = head to make it circular.
Step 4: Else (list is not empty):
    a. Traverse to the last node of the list.
    b. Set newNode->next = head.
    c. Update the last node’s next to point to newNode.
    d. Move head pointer to newNode.
Step 5: Stop

C program

#include<stdio.h> 
#include<conio.h>
#include<stdlib.h>
struct node{
	int data;
	struct node *next;
	};
struct node *head=NULL;
struct node* createNode(){
	struct node *newNode = (struct node *)malloc(sizeof(struct node));
    return (newNode);
    }

void insertNodeAtBegin(){
    struct node *newNode, *temp, *ptr1, *ptr2;
    newNode=createNode();
    printf("Enter a data to insert at begining:");
    scanf("%d",&newNode->data);
    newNode->next=NULL;
    if(head==NULL){
	    head=newNode;
	    head->next=head;
    }
    else{
	    ptr1=head;
	    ptr2=head;
	    while(ptr1->next!=head){
		    ptr1=ptr1->next;
	    }
	    ptr1->next=newNode;
	    head=newNode;
	    head->next=ptr2;
    }
}

void viewList(){
	struct node* temp=head;
	if(temp==NULL){
		printf("list is empty");
	}
	else{
	    printf("Data in circular linked list are:\n");
		while(temp->next!=head)
		{
			printf("%d\t",temp->data);
			temp=temp->next;
		}
		printf("%d \t",temp->data);
	}
}

int menu(){
    int choice;
    printf("\n 1. Insert at begining");
    printf("\n 2. Travesre/View List");
    printf("\n 3. exit");
    printf("\n Please enter your choice: \t");
    scanf("%d",&choice);
    return(choice);
}
 void main(){
    printf("Insert a node in Beginning of circular linked list"); 
    while(1){
        switch(menu()){
            case 1:
                insertNodeAtBegin();
                break;
            case 2:
                viewList();
                break;
            case 3:
                exit(0);
            default:
                printf("invalid choice");   
        }
        getch();
    }  
}

Output:

Insert a node in Beginning of circular linked list
 1. Insert at begining
 2. Travesre/View List
 3. exit
 Please enter your choice:      1
Enter a data to insert at begining:4

 1. Insert at begining
 2. Travesre/View List
 3. exit
 Please enter your choice:      1
Enter a data to insert at begining:7

 1. Insert at begining
 2. Travesre/View List
 3. exit
 Please enter your choice:      1
Enter a data to insert at begining:9

 1. Insert at begining
 2. Travesre/View List
 3. exit
 Please enter your choice:      1
Enter a data to insert at begining:5

 1. Insert at begining
 2. Travesre/View List
 3. exit
 Please enter your choice:      2
Data in circular linked list are:
5       9       7       4 
 1. Insert at begining
 2. Travesre/View List
 3. exit
 Please enter your choice:      3

Explanation of Code

1. Structure Definition

struct node {
    int data;
    struct node *next;
};
struct node *head = NULL;
  • Each node contains:
    • data: integer value
    • next: pointer to the next node
  • head points to the first node of the circular linked list.

2. Node Creation

struct node* createNode() {
    struct node *newNode = (struct node *)malloc(sizeof(struct node));
    return newNode;
}
  • Dynamically allocates memory for a new node.
  • Returns pointer to the newly created node.

3. Insert Node at Beginning

void insertNodeAtBegin() {
    struct node *newNode, *temp, *ptr1, *ptr2;
    newNode = createNode();
    printf("Enter a data to insert at beginning: ");
    scanf("%d", &newNode->data);
    newNode->next = NULL;

    if (head == NULL) {           // if list is empty
        head = newNode;
        head->next = head;        // points to itself
    } else {
        ptr1 = head;
        ptr2 = head;
        while (ptr1->next != head) {  // move to last node
            ptr1 = ptr1->next;
        }
        ptr1->next = newNode;     // last node points to new node
        head = newNode;           // update head
        head->next = ptr2;        // new node points to previous head
    }
}

Logic:

  • If list is empty → new node points to itself and becomes head.
  • Otherwise → traverse to last node, link it to new node, update head, and new node points to old head.

4. View / Traverse List

void viewList() {
    struct node* temp = head;
    if (temp == NULL) {
        printf("List is empty");
    } else {
        printf("Data in circular linked list are:\n");
        while (temp->next != head) {
            printf("%d\t", temp->data);
            temp = temp->next;
        }
        printf("%d\t", temp->data);  // print last node
    }
}
  • Traverses from head and prints all nodes until it returns to head.

5. Menu Function

int menu() {
    int choice;
    printf("\n 1. Insert at beginning");
    printf("\n 2. Traverse/View List");
    printf("\n 3. Exit");
    printf("\n Please enter your choice: ");
    scanf("%d", &choice);
    return choice;
}
  • Provides user options to insert, view, or exit.

6. Main Function

void main() {
    printf("Insert a node at Beginning of circular linked list");
    while (1) {
        switch(menu()) {
            case 1:
                insertNodeAtBegin();
                break;
            case 2:
                viewList();
                break;
            case 3:
                exit(0);
            default:
                printf("Invalid choice");
        }
        getch();
    }
}
  • Runs continuously until user selects exit.
  • Calls functions based on menu choice.

Time & Space Complexity

OperationBest CaseAverage CaseWorst CaseSpace Complexity
Insert at Beginning (empty list)O(1)O(1)O(1)O(1)
Insert at Beginning (non-empty)O(n)O(n)O(n)O(1)
Traverse / View ListO(n)O(n)O(n)O(1)

Insert a node at end of Circular Linked list

Algorithm

  1. Start.
  2. Create a new node and input its data.
  3. If head == NULL → make new node point to itself and set head = new node.
  4. Else → traverse the list to reach the last node.
  5. Link the last node’s next to new node.
  6. Link new node’s next to head.
  7. End

C Program

#include<stdio.h> 
#include<conio.h>
#include<stdlib.h>
struct node{
	int data;
	struct node *next;
	};
struct node *head=NULL;
struct node* createNode(){
	struct node *newNode = (struct node *)malloc(sizeof(struct node));
    return (newNode);
    }

void insertNodeAtEnd(){
	struct node *temp,*ptr;
	temp=createNode();
	printf("Enter a data to insert at end:");
	scanf("%d",&temp->data);
	temp->next=NULL;
	if(head==NULL){
		head=temp;
		head->next=head;
	}
	else{
		ptr=head;
		while(ptr->next!=head){
			ptr=ptr->next;
		}
	    ptr->next=temp;
	    temp->next=head;
	}
}

void viewList(){
	struct node* temp=head;
	if(temp==NULL){
		printf("list is empty");
	}
	else{
	    printf("Data in circular linked list are:\n");
		while(temp->next!=head)
		{
			printf("%d\t",temp->data);
			temp=temp->next;
		}
		printf("%d \t",temp->data);
	}
}

int menu(){
    int choice;
    printf("\n 1. Insert at end");
    printf("\n 2. Travesre/View List");
    printf("\n 3. exit");
    printf("\n Please enter your choice: \t");
    scanf("%d",&choice);
    return(choice);
}
 void main(){
    printf("Insert a node at end of Circular Linked list");
    while(1){
        switch(menu()){
            case 1:
                insertNodeAtEnd();
                break;
            case 2:
                viewList();
                break;
            case 3:
                exit(0);
            default:
                printf("invalid choice");   
        }
        getch();
    }  
}

Output:

Insert a node at end of Circular Linked list
 1. Insert at end
 2. Travesre/View List
 3. exit
 Please enter your choice:      1
Enter a data to insert at end:4

 1. Insert at end
 2. Travesre/View List
 3. exit
 Please enter your choice:      1
Enter a data to insert at end:6

 1. Insert at end
 2. Travesre/View List
 3. exit
 Please enter your choice:      1
Enter a data to insert at end:3

 1. Insert at end
 2. Travesre/View List
 3. exit
 Please enter your choice:      1
Enter a data to insert at end:2

 1. Insert at end
 2. Travesre/View List
 3. exit
 Please enter your choice:      2
Data in circular linked list are:
4       6       3       2 
 1. Insert at end
 2. Travesre/View List
 3. exit
 Please enter your choice:      3

Explanation of Code

1. Structure Definition

struct node {
    int data;
    struct node *next;
};
struct node *head = NULL;
  • Each node contains:
    • data: integer value
    • next: pointer to the next node
  • head points to the first node of the circular linked list.

2. Node Creation

struct node* createNode() {
    struct node *newNode = (struct node *)malloc(sizeof(struct node));
    return newNode;
}
  • Dynamically allocates memory for a new node.
  • Returns pointer to the newly created node.

3. Insert Node at End

void insertNodeAtEnd() {
    struct node *temp, *ptr;
    temp = createNode();
    printf("Enter a data to insert at end: ");
    scanf("%d", &temp->data);
    temp->next = NULL;

    if (head == NULL) {          // if list is empty
        head = temp;
        head->next = head;       // first node points to itself
    } else {
        ptr = head;
        while (ptr->next != head) {  // traverse to last node
            ptr = ptr->next;
        }
        ptr->next = temp;         // link last node to new node
        temp->next = head;        // new node points to head
    }
}

 Logic:

  • If the list is empty → the new node becomes head and points to itself.
  • Otherwise → traverse to the last node, insert new node, and link it back to head.

4. View / Traverse List

void viewList() {
    struct node* temp = head;
    if (temp == NULL) {
        printf("List is empty");
    } else {
        printf("Data in circular linked list are:\n");
        while (temp->next != head) {
            printf("%d\t", temp->data);
            temp = temp->next;
        }
        printf("%d\t", temp->data);  // print last node
    }
}
  • Traverses from head and prints all nodes until it comes back to head.

5. Menu Function

int menu() {
    int choice;
    printf("\n 1. Insert at end");
    printf("\n 2. Traverse/View List");
    printf("\n 3. Exit");
    printf("\n Please enter your choice: ");
    scanf("%d", &choice);
    return choice;
}
  • Provides user options → insert at end, view, or exit.

6. Main Function

void main() {
    printf("Insert a node at end of Circular Linked list");
    while (1) {
        switch(menu()) {
            case 1:
                insertNodeAtEnd();
                break;
            case 2:
                viewList();
                break;
            case 3:
                exit(0);
            default:
                printf("Invalid choice");
        }
        getch();
    }
}
  • Runs continuously until user selects exit.
  • Calls functions based on menu choice.

Time & Space Complexity

OperationBest CaseAverage CaseWorst CaseSpace Complexity
Insert at End (empty list)O(1)O(1)O(1)O(1)
Insert at End (non-empty list)O(n)O(n)O(n)O(1)
Traverse / View ListO(n)O(n)O(n)O(1)

Insert a node at a given position in Circular Linked List

Algorithm

  1. Start.
  2. Create a new node and input its data.
  3. Insert at end:
    • If list is empty → node points to itself, set head.
    • Else → traverse to last node, link new node, and link back to head.
  4. Insert at given position:
    • If position = 1 → same as inserting at beginning.
    • Else → traverse to (position-1) node and insert new node.
    • Invalid position → show error.
  5. End.

C Program

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>

struct node {
    int data;
    struct node *next;
};

struct node *head = NULL;

struct node* createNode() {
    struct node *newNode = (struct node *)malloc(sizeof(struct node));
    return newNode;
}

void insertNodeAtEnd() {
    struct node *temp, *ptr;
    temp = createNode();
    printf("Enter a data to insert at end: ");
    scanf("%d", &temp->data);
    temp->next = NULL;

    if (head == NULL) {
        head = temp;
        head->next = head;
    } else {
        ptr = head;
        while (ptr->next != head) {
            ptr = ptr->next;
        }
        ptr->next = temp;
        temp->next = head;
    }
}

void insertNodeAtLocation() {
    int pos, i = 1;
    struct node *temp, *ptr;
    temp = createNode();
    printf("Enter position to insert: ");
    scanf("%d", &pos);
    printf("Enter data to insert at position %d: ", pos);
    scanf("%d", &temp->data);
    temp->next = NULL;

    if (pos == 1) {
        if (head == NULL) {
            head = temp;
            head->next = head;
        } else {
            ptr = head;
            while (ptr->next != head) {
                ptr = ptr->next;
            }
            temp->next = head;
            head = temp;
            ptr->next = head;
        }
    } else {
        ptr = head;
        while (i < pos - 1 && ptr->next != head) {
            ptr = ptr->next;
            i++;
        }
        if (i == pos - 1) {
            temp->next = ptr->next;
            ptr->next = temp;
        } else {
            printf("Invalid position!\n");
            free(temp);
        }
    }
}

void viewList() {
    struct node* temp = head;
    if (temp == NULL) {
        printf("List is empty\n");
    } else {
        printf("Data in circular linked list are:\n");
        while (temp->next != head) {
            printf("%d\t", temp->data);
            temp = temp->next;
        }
        printf("%d\t", temp->data);
    }
}

int menu() {
    int choice;
    printf("\n--- MENU ---");
    printf("\n1. Insert at end");
    printf("\n2. Insert at a given location");
    printf("\n3. Traverse/View List");
    printf("\n4. Exit");
    printf("\nEnter your choice: ");
    scanf("%d", &choice);
    return choice;
}

void main() {
    printf("Insertion in Circular Linked List\n");
    while (1) {
        switch (menu()) {
            case 1:
                insertNodeAtEnd();
                break;
            case 2:
                insertNodeAtLocation();
                break;
            case 3:
                viewList();
                break;
            case 4:
                exit(0);
            default:
                printf("Invalid choice\n");
        }
        getch();
    }
}

Output:

Insertion in Circular Linked List

--- MENU ---
1. Insert at end
2. Insert at a given location
3. Traverse/View List
4. Exit
Enter your choice: 1
Enter a data to insert at end: 4

--- MENU ---
1. Insert at end
2. Insert at a given location
3. Traverse/View List
4. Exit
Enter your choice: 1
Enter a data to insert at end: 6

--- MENU ---
1. Insert at end
2. Insert at a given location
3. Traverse/View List
4. Exit
Enter your choice: 1
Enter a data to insert at end: 8

--- MENU ---
1. Insert at end
2. Insert at a given location
3. Traverse/View List
4. Exit
Enter your choice: 1
Enter a data to insert at end: 3

--- MENU ---
1. Insert at end
2. Insert at a given location
3. Traverse/View List
4. Exit
Enter your choice: 3
Data in circular linked list are:
4       6       8       3
--- MENU ---
1. Insert at end
2. Insert at a given location
3. Traverse/View List
4. Exit
Enter your choice: 2
Enter position to insert: 2
Enter data to insert at position 2: 8

--- MENU ---
1. Insert at end
2. Insert at a given location
3. Traverse/View List
4. Exit
Enter your choice: 3
Data in circular linked list are:
4       8       6       8       3
--- MENU ---
1. Insert at end
2. Insert at a given location
3. Traverse/View List
4. Exit
Enter your choice: 3

Explanation of Code

1. Structure Definition

struct node {
    int data;
    struct node *next;
};
struct node *head = NULL;
  • Each node contains:
    • data: integer value
    • next: pointer to the next node
  • head points to the first node of the circular linked list.

2. Node Creation

struct node* createNode() {
    struct node *newNode = (struct node *)malloc(sizeof(struct node));
    return newNode;
}
  • Dynamically allocates memory for a new node.
  • Returns pointer to the newly created node.

3. Insert Node at End

void insertNodeAtEnd() {
    struct node *temp, *ptr;
    temp = createNode();
    printf("Enter a data to insert at end: ");
    scanf("%d", &temp->data);
    temp->next = NULL;

    if (head == NULL) {          // if list is empty
        head = temp;
        head->next = head;       // first node points to itself
    } else {
        ptr = head;
        while (ptr->next != head) {  // traverse to last node
            ptr = ptr->next;
        }
        ptr->next = temp;         // link last node to new node
        temp->next = head;        // new node points to head
    }
}

 Logic:

  • If list is empty → new node becomes head and points to itself.
  • Otherwise → traverse to last node, insert new node, and link it back to head.

4. Insert Node at a Given Location

void insertNodeAtLocation() {
    int pos, i = 1;
    struct node *temp, *ptr;
    temp = createNode();
    printf("Enter position to insert: ");
    scanf("%d", &pos);
    printf("Enter data to insert at position %d: ", pos);
    scanf("%d", &temp->data);
    temp->next = NULL;

    if (pos == 1) {   // Insert at beginning
        if (head == NULL) {
            head = temp;
            head->next = head;
        } else {
            ptr = head;
            while (ptr->next != head) {
                ptr = ptr->next;   // last node
            }
            temp->next = head;
            head = temp;          // update head
            ptr->next = head;     // last node points to new head
        }
    } else {  // Insert at position > 1
        ptr = head;
        while (i < pos - 1 && ptr->next != head) {
            ptr = ptr->next;
            i++;
        }
        if (i == pos - 1) {
            temp->next = ptr->next;
            ptr->next = temp;    // link node at position
        } else {
            printf("Invalid position!\n");
            free(temp);
        }
    }
}

Logic:

  • Position = 1: behaves like inserting at the beginning.
  • Position > 1: traverse to (position-1) node and insert new node.
  • Invalid position → prints error and frees memory.

5. View / Traverse List

void viewList() {
    struct node* temp = head;
    if (temp == NULL) {
        printf("List is empty\n");
    } else {
        printf("Data in circular linked list are:\n");
        while (temp->next != head) {
            printf("%d\t", temp->data);
            temp = temp->next;
        }
        printf("%d\t", temp->data);  // print last node
    }
}
  • Traverses from head and prints all nodes until returning to head.

6. Menu Function

int menu() {
    int choice;
    printf("\n--- MENU ---");
    printf("\n1. Insert at end");
    printf("\n2. Insert at a given location");
    printf("\n3. Traverse/View List");
    printf("\n4. Exit");
    printf("\nEnter your choice: ");
    scanf("%d", &choice);
    return choice;
}
  • Provides user options → insert at end, insert at position, view, or exit.

7. Main Function

void main() {
    printf("Insertion in Circular Linked List\n");
    while (1) {
        switch (menu()) {
            case 1:
                insertNodeAtEnd();
                break;
            case 2:
                insertNodeAtLocation();
                break;
            case 3:
                viewList();
                break;
            case 4:
                exit(0);
            default:
                printf("Invalid choice\n");
        }
        getch();
    }
}
  • Runs continuously until user selects exit.
  • Calls respective functions based on user choice.

Time & Space Complexity

OperationBest CaseAverage CaseWorst CaseSpace Complexity
Insert at End (empty list)O(1)O(1)O(1)O(1)
Insert at End (non-empty list)O(n)O(n)O(n)O(1)
Insert at Position = 1O(1)O(n)O(n)O(1)
Insert at Position > 1O(n)O(n)O(n)O(1)
Traverse / View ListO(n)O(n)O(n)O(1)

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