Circular Linked List in C – Insert and Delete Operations

A circular linked list in C is a type of linked list where the last node points back to the first node, forming a circular structure. This data structure is useful in applications where traversal needs to be continuous or repeated in a loop.

In this tutorial, we will implement a circular linked list in C and perform the following operations:

• Insert a node at the end of the linked list
• Insert a node before a specified position
• Delete the first node of the linked list
• Delete a node after a specified position

These operations help strengthen understanding of pointer manipulation and circular list behavior in C programming.

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C Program for Circular Linked List in C

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

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

struct Node* head = NULL;

void insertEnd(int value) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = value;

    if (head == NULL) {
        head = newNode;
        newNode->next = head;
        return;
    }

    struct Node* temp = head;
    while (temp->next != head)
        temp = temp->next;

    temp->next = newNode;
    newNode->next = head;
}

void insertBeforePosition(int value, int pos) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = value;

    if (pos == 1) {
        struct Node* temp = head;
        while (temp->next != head)
            temp = temp->next;
        newNode->next = head;
        temp->next = newNode;
        head = newNode;
        return;
    }

    struct Node* temp = head;
    int i = 1;
    while (i < pos - 1 && temp->next != head) {
        temp = temp->next;
        i++;
    }

    if (i != pos - 1) {
        printf("Invalid position\n");
        return;
    }

    newNode->next = temp->next;
    temp->next = newNode;
}

void deleteFirst() {
    if (head == NULL) return;

    struct Node* temp = head;

    if (head->next == head) {
        free(head);
        head = NULL;
        return;
    }

    struct Node* last = head;
    while (last->next != head)
        last = last->next;

    head = head->next;
    last->next = head;
    free(temp);
}

void deleteAfterPosition(int pos) {
    if (head == NULL) return;

    struct Node* temp = head;
    int i = 1;

    while (i < pos && temp->next != head) {
        temp = temp->next;
        i++;
    }

    if (temp->next == head) {
        printf("No node exists after position %d\n", pos);
        return;
    }

    struct Node* del = temp->next;
    temp->next = del->next;

    if (del == head)
        head = del->next;

    free(del);
}

void display() {
    if (head == NULL) {
        printf("List is empty\n");
        return;
    }

    struct Node* temp = head;
    do {
        printf("%d -> ", temp->data);
        temp = temp->next;
    } while (temp != head);
    printf("HEAD\n");
}

int main() {
    insertEnd(10);
    insertEnd(20);
    insertEnd(30);
    display();

    insertBeforePosition(5, 1);
    display();

    deleteFirst();
    display();

    deleteAfterPosition(2);
    display();

    return 0;
}

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Why Use Circular Linked List in C?

Using a circular linked list in C offers advantages in real-time applications like buffering, task scheduling, and multiplayer games. Since the last node connects back to the first, it helps in continuous looping structures.