Singly Circular Linked List

CASES IN INSERTION

1. At Start of linkedlist
2. At End of linkedlist
3. After a defined(key) element
4. Before a defined(key) element

CASES IN DELETION

1. Delete Elements from Start
2. Delete Elements from End
3. Delete Inputted Elements

CODE

// Generated by ChatGPT
#include <stdio.h>
#include <stdlib.h>

// Node structure
typedef struct NODE
{
    int data;
    struct NODE *next;
};

// Global variables
NODE *head = NULL;

// Function to add a node at the start of the list
void addAtStart(int data)
{
    NODE *newNode = (NODE *)malloc(sizeof(NODE));
    newNode->data = data;
    newNode->next = head;
    head = newNode;
}

// Function to add a node at the end of the list
void addAtEnd(int data)
{
    NODE *newNode = (NODE *)malloc(sizeof(NODE));
    newNode->data = data;
    newNode->next = NULL;

    if (head == NULL)
    {
        head = newNode;
        return;
    }

    NODE *curr = head;
    while (curr->next != NULL)
    {
        curr = curr->next;
    }
    curr->next = newNode;
}

// Function to add a node before a given node
void addBefore(int key, int data)
{
    NODE *newNode = (NODE *)malloc(sizeof(NODE));
    newNode->data = data;
    newNode->next = NULL;

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

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

    NODE *curr = head;
    while (curr->next != NULL && curr->next->data != key)
    {
        curr = curr->next;
    }

    if (curr->next == NULL)
    {
        printf("Key not found\n");
        return;
    }

    newNode->next = curr->next;
    curr->next = newNode;
}

// Function to add a node after a given node
void addAfter(int key, int data)
{
    NODE *newNode = (NODE *)malloc(sizeof(NODE));
    newNode->data = data;
    newNode->next = NULL;

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

    NODE *curr = head;
    while (curr != NULL && curr->data != key)
    {
        curr = curr->next;
    }

    if (curr == NULL)
    {
        printf("Key not found\n");
        return;
    }

    newNode->next = curr->next;
    curr->next = newNode;
}

// Function to delete the first node of the list
void deleteStart()
{
    if (head == NULL)
    {
        printf("List is empty\n");
        return;
    }

    NODE *temp = head;
    head = head->next;
    free(temp);
}

// Function to delete the last node of the list
void deleteEnd()
{
    if (head == NULL)
    {
        printf("List is empty\n");
        return;
    }

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

    NODE *curr = head;
    while (curr->next->next != NULL)
    {
        curr = curr->next;
    }
    free(curr->next);
    curr->next = NULL;
}

// Function to delete a node with a given key
void deleteKey(int key)
{
    if (head == NULL)
    {
        printf("List is empty\n");
        return;
    }

    if (head->data == key)
    {
        NODE *temp = head;
        head = head->next;
        free(temp);
        return;
    }

    NODE *curr = head;
    while (curr->next != NULL && curr->next->data != key)
    {
        curr = curr->next;
    }

    if (curr->next == NULL)
    {
        printf("Key not found\n");
        return;
    }

    NODE *temp = curr->next;
    curr->next = curr->next->next;
    free(temp);
}

// Function to print the list
void printList()
{
    NODE *curr = head;
    while (curr != NULL)
    {
        printf("%d ", curr->data);
        curr = curr->next;
    }
    printf("\n");
}

// Main function
int main()
{
    int choice, data, key;
    while (1)
    {
        printf("\n1. Add at start\n2. Add at end\n3. Add before\n4. Add after\n");
        printf("5. Delete start\n6. Delete end\n7. Delete key\n8. Print list\n9. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        switch (choice)
        {
        case 1:
            printf("Enter data to add at start: ");
            scanf("%d", &data);
            addAtStart(data);
            break;
        case 2:
            printf("Enter data to add at end: ");
            scanf("%d", &data);
            addAtEnd(data);
            break;
        case 3:
            printf("Enter key before which to add data: ");
            scanf("%d", &key);
            printf("Enter data to add before %d: ", key);
            scanf("%d", &data);
            addBefore(key, data);
            break;
        case 4:
            printf("Enter key after which to add data: ");
            scanf("%d", &key);
            printf("Enter data to add after %d: ", key);
            scanf("%d", &data);
            addAfter(key, data);
            break;
        case 5:
            deleteStart();
            break;
        case 6:
            deleteEnd();
            break;
        case 7:
            printf("Enter key to delete: ");
            scanf("%d", &key);
            deleteKey(key);
            break;
        case 8:
            printf("List: ");
            printList();
            break;
        case 9:
            exit(0);
        default:
            printf("Invalid choice\n");
        }
    }

    return 0;
}