C program to Swap Two Nodes in 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.

Here is a source code of the C program to interchange the two adjacent nodes given a circular linked list. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/*
```

 * C Program to Interchange the two Adjacent Nodes given a circular

```
 * Linked List 
```
```
 */
```
```
#include <stdio.h>
```
```
#include <stdlib.h>
```
```
 
```
```
struct node
```
```
{
```
```
    int num;
```
```
    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 num;
```
```
 
```

    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", &num);
```
```
    change(&p, num - 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 num)

```
{
```
```
    struct node *p, *q, *r;
```
```
 
```
```
    p = q = r = *head;
```
```
    p = p->next->next;
```
```
    q = q->next;
```
```
    while (num != 0)
```
```
    {
```
```
        r = q;
```
```
        q = p;
```
```
        p = p->next;
```
```
        num--;
```
```
    }
```
```
    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->num = 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->num);
```
```
    temp = temp->next;
```
```
    while (head != temp)
```
```
    {
```
```
        printf("%d\t", temp->num);
```
```
        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;
```
```
    }
```
```
}
```

$ gcc interchangenode.c 
$ ./a.out
Enter data into the list
Enter number: 1
Do you wish to continue [1/0]: 1
Enter number: 2
Do you wish to continue [1/0]: 1
Enter number: 3
Do you wish to continue [1/0]: 1
Enter number: 4
Do you wish to continue [1/0]: 1
Enter number: 5
Do you wish to continue [1/0]: 0
 
Circular list generated
Displaying the list elements
1	2	3	4	5	
Enter node position to interchange with it's adjacent: 2
After interchanging, Displaying the list elements
1	3	2	4	5

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