Code:
#include stdio.h
#include stdlib.h
struct node
{
int num;
struct node *next;
};
void create(struct node **);
void release(struct node **);
void change(struct node **, int, int);
void display(struct node *);
int main()
{
struct node *p = NULL;
int num1, num2;
printf("Enter data into the list\n");
create(&p);
printf("Circular list generated\n");
display(p);
printf("Enter node position: ");
scanf("%d", &num1);
printf("Enter node position to exchange with: ");
scanf("%d", &num2);
change(&p, num1 - 2, num2 - 2);
printf("After interchanging, ");
display(p);
release (&p);
return 0;
}
void change(struct node **head, int num1, int num2)
{
struct node *p1, *q1, *r1;
struct node *p2, *q2, *r2;
p1 = q1 = r1 = *head;
p2 = q2 = r2 = *head;
if (num1 == num2)
{
return;
}
else if ((p1->next == NULL && num1 > 0) || (p1->next->next == NULL && num1 > 1))
{
printf("List smaller than entered node position.\n");
}
else if ((p2->next == NULL && num2 > 0) || (p2->next->next == NULL && num2 > 1))
{
printf("List smaller than entered node position.\n");
}
else
{
if (num1 >=0 && num2 >= 0)
{
p1 = p1->next->next;
q1 = q1->next;
while (num1 > 0)
{
r1 = q1;
q1 = p1;
p1 = p1->next;
num1--;
}
p2 = p2->next->next;
q2 = q2->next;
while (num2 > 0)
{
r2 = q2;
q2 = p2;
p2 = p2->next;
num2--;
}
r2->next = q1;
q2->next = p1;
r1->next = q2;
q1->next = p2;
}
else if (num1 == -1)
{
p2 = p2->next->next;
q2 = q2->next;
while (num2 > 0)
{
r2 = q2;
q2 = p2;
p2 = p2->next;
num2--;
}
if (p1->next != q2)
{
q2->next = p1->next;
p1->next = p2;
r2->next = p1;
}
else
{
p1->next = q2->next;
q2->next = p1;
}
*head = q2;
}
else if (num2 == -1)
{
p1 = p1->next->next;
q1 = q1->next;
while (num1 > 0)
{
r1 = q1;
q1 = p1;
p1 = p1->next;
num1--;
}
if (p2->next != q1)
{
q1->next = p2->next;
p2->next = p1;
r1->next = p2;
}
else
{
p2->next = q1->next;
q1->next = p2;
}
*head = q1;
}
}
}
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");
while (temp != NULL)
{
printf("%d\t", temp->num);
temp = temp->next;
}
printf("\n");
}
void release(struct node **head)
{
struct node *temp = *head;
*head = (*head)->next;
while ((*head) != NULL)
{
free(temp);
temp = *head;
(*head) = (*head)->next;
}
}
Output:
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: 2
Enter node position to exchange with: 4
After interchanging, Displaying the list elements
1 4 3 2 5
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