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Program to Interchange the two Adjacent Nodes given a circular Linked List



Program to Interchange the two Adjacent Nodes given a circular Linked List

This C Program interchanges the two adjacent nodes given a circular linked list. The nodes exchanged are as per user's entered node position.

    #include <stdio.h>

    #include <stdlib.h>

    struct node

    {

        int j;

        struct node *next;

    };

    void create(struct node **);

    void tocircular(struct node **);

    void release(struct node **);

    void change(struct node **, int);

    void display(struct node *);

    int main()

    {

        struct node *p = NULL;

        int j;

        printf("Enter data into the list\n");

        create(&p);

        tocircular(&p);

        printf("Circular list generated\n");

        display(p);

        printf("Enter node position to interchange with it's adjacent: ");

        scanf("%d", &j);

        change(&p, j - 2);

        printf("After interchanging, ");

        display(p);

        release (&p);

        return 0;

    }

    void tocircular(struct node **p)

    {

        struct node *rear;

        rear = *p;

        while (rear->next != NULL)

        {

            rear = rear->next;

        }

        rear->next = *p;

        /*After this the singly linked list is now circular*/

    }

    void change(struct node **head, int j)

    {

        struct node *p, *q, *r;

        p = q = r = *head;

        p = p->next->next;

        q = q->next;

        while (j != 0)

        {

            r = q;

            q = p;

            p = p->next;

            j--;

        }

        r->next = p;

        q->next = p->next;

        p->next = q;   

    }

    void create(struct node **head)

    {

        int c, ch;

        struct node *temp, *rear;

        do

        {

            printf("Enter number: ");

            scanf("%d", &c);

            temp = (struct node *)malloc(sizeof(struct node));

            temp->j = c;

            temp->next = NULL;

            if (*head == NULL)

            {

                *head = temp;

            }

            else

            {

                rear->next = temp;

            }

            rear = temp;

            printf("Do you wish to continue [1/0]: ");

            scanf("%d", &ch);

        } while (ch != 0);

        printf("\n");

    }

    void display(struct node *head)

    {

        struct node *temp = head;

        printf("Displaying the list elements\n");

        printf("%d\t", temp->j);

        temp = temp->next;

        while (head != temp)

        {

            printf("%d\t", temp->j);

            temp = temp->next;

        }

        printf("\n");

    }

    void release(struct node **head)

    {

        struct node *temp = *head;

        temp = temp->next;

        (*head)->next = NULL;

        (*head) = temp->next;

        while ((*head) != NULL)

        {

            free(temp);

            temp = *head;

            (*head) = (*head)->next;

        }

    }