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circular_linked_list.c
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circular_linked_list.c
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#include<stdio.h>
#include<stdlib.h>
struct node* create(struct node* start);
struct node* display(struct node* start);
struct node* insertatbeg(struct node* start);
struct node* insertatend(struct node* start);
struct node* insertbeforepos(struct node* start);
struct node* insertafterpos(struct node* start);
struct node* deleteatbeg(struct node* start);
struct node* deleteatend(struct node* start);
struct node* deletebeforepos(struct node* start);
struct node* deleteafterpos(struct node* start);
struct node* reverse(struct node* start);
struct node* size(struct node* start);
struct node* search(struct node* start);
struct node{ int data; struct node *next; };
struct node *start=NULL; void main()
{
int option;
printf("1.Create a circular linked list \n");
printf("2.Display a circular linked list \n");
printf("3.Insert at the begining of a circular linked list \n");
printf("4.Insert at the end of a circular linked list \n");
printf("5.Insert before a particular position \n");
printf("6.Insert after a particular position \n");
printf("7.Delete a node at the begining of a circular linked list \n");
printf("8.Delete a node at the end of a circular linked list \n");
printf("9.Delete before a particular position \n");
printf("10.Delete after a particular position \n");
printf("11.Calculate the number of elements of the circular linked list \n");
printf("12.Search an element in the circular linked list \n");
printf("13.Reverse a circular linked list \n");
while(1)
{
printf("Choose an option from the following: \n");
scanf("%d",&option);
switch(option)
{
case 1:
printf("Enter values and to finish entering, press -1 on terminal!\n");
start = create(start);
break;
case 2:
display(start);
break;
case 3:
start = insertatbeg(start);
display(start);
break;
case 4:
start = insertatend(start);
display(start);
break;
case 5:
start = insertbeforepos(start);
display(start);
break;
case 6:
start = insertafterpos(start);
display(start);
break;
case 7:
start = deleteatbeg(start);
display(start);
break;
case 8:
start = deleteatend(start);
display(start);
break;
case 9:
start = deletebeforepos(start);
display(start);
break;
case 10:
start = deleteafterpos(start);
display(start);
break;
case 13:
start = reverse(start);
display(start);
break;
case 11:
start=size(start);
break;
case 12:
start=search(start);
break;
default:
printf("Enter correct option!!\n");
}
}
}
struct node* create(struct node* start)
{
int num;
struct node *newnode,*ptr;
// printf("Enter data:\n");
scanf("%d",&num);
while(num!=-1)
{
newnode=(struct node*)calloc(1,sizeof(struct node));
newnode->data=num;
if(start==NULL)
{
start=newnode;
newnode->next=start;
}
else
{ ptr=start;
while(ptr->next!=start)
{
ptr=ptr->next;
}
ptr->next=newnode;
newnode->next=start;
}
scanf("%d",&num);
}
return start;
}
struct node* display(struct node* start)
{
struct node *ptr;
ptr=start;
if (start == NULL)
{
//printf("Circular linked list is empty.\n");
return start;
}
do
{ printf("%d --> ", ptr->data);
ptr = ptr->next;
}
while (ptr != start);
printf("START");
printf("\n");
return start;
}
struct node* insertatbeg(struct node* start)
{
struct node *newnode, *ptr;
int num;
printf("Enter the value you want to insert at the beginning: ");
scanf("%d", &num);
newnode = (struct node*)calloc(1, sizeof(struct node));
newnode->data = num;
if (start == NULL)
{
newnode->next = newnode;
// Circular link to itself for the first node
} else
{
ptr = start;
while (ptr->next != start)
{
ptr = ptr->next;
}
ptr->next = newnode;
newnode->next = start;
}
start = newnode;
// Update the start pointer return start;
}
struct node* insertatend(struct node* start)
{ struct node *newnode,*ptr;
int num;
printf("Enter the value you want to insert at end: ");
scanf("%d",&num);
ptr=start;
newnode=(struct node*)calloc(1,sizeof(struct node));
newnode->data=num;
while(ptr->next!=start)
{ ptr=ptr->next;
}
ptr->next=newnode;
newnode->next=start;
return start;
}
struct node* insertbeforepos(struct node* start)
{ struct node *newnode,*ptr,*preptr;
int num;
int val;
printf("Ente the value before which you want to insert: \n");
scanf("%d",&val);
printf("Enter the value to be inserted: \n");
scanf("%d",&num);
ptr=start;
newnode=(struct node*)calloc(1,sizeof(struct node));
newnode->data=num;
while(ptr->data!=val)
{
preptr=ptr;
ptr=ptr->next;
}
preptr->next=newnode;
newnode->next=ptr;
return start; }
struct node*
insertafterpos(struct node* start)
{
struct node *newnode,*ptr,*preptr;
int num;
int val;
printf("Enter the value after which you want to insert: \n");
scanf("%d",&val);
printf("Enter the value to be inserted: \n");
scanf("%d",&num);
ptr=start;
newnode=(struct node*)calloc(1,sizeof(struct node));
newnode->data=num;
while(ptr->data!=val)
{ ptr=ptr->next;
} preptr=ptr->next;
ptr->next=newnode;
newnode->next=preptr;
return start;
} struct node* deleteatbeg(struct node* start)
{
if (start == NULL)
{ //printf("Circular linked list is empty. Cannot delete.\n");
return start;
}
struct node *ptr = start;
if (start->next == start)
{
free(start);
start = NULL;
}
else {
while (ptr->next != start)
{ ptr = ptr->next;
} ptr->next = start->next;
struct node *temp = start;
start = start->next;
free(temp);
} return start;
} struct node* deleteatend(struct node* start)
{ struct node *ptr,*preptr;
ptr=start;
while(ptr->next!=start)
{
preptr=ptr;
ptr=ptr->next;
}
preptr->next=start;
free(ptr);
return start;
}
struct node* deletebeforepos(struct node* start)
{
struct node *ptr,*preptr,*p1;
ptr=start;
preptr=start;
int val;
printf("Enter the value before which you want to delete the node: \n");
scanf("%d",&val);
while(ptr->data!=val)
{ p1=preptr;
preptr=ptr;
ptr=ptr->next;
}
p1->next=ptr;
free(preptr);
return start;
} struct node* deleteafterpos(struct node* start)
{ struct node *ptr,*preptr;
ptr=start;
preptr=start;
int val;
printf("Enter the value after which you want to delete the node: \n");
scanf("%d",&val);
while(ptr->data!=val)
{ ptr=ptr->next;
} preptr=ptr->next;
ptr->next=preptr->next;
free(preptr);
return start;
} struct node* size(struct node* start)
{
struct node *ptr;
ptr=start;
int i=1;
while(ptr->next!=start)
{ ptr=ptr->next;
i++;
}
printf("The linked list has %d elements. \n",i);
return start;
}
struct node* reverse(struct node* start)
{
if (start == NULL || start->next == start)
{
return start;
} struct node *prevnode = NULL;
struct node *currentnode = start;
struct node *nextnode = NULL;
do
{ nextnode = currentnode->next;
currentnode->next = prevnode;
prevnode = currentnode;
currentnode = nextnode;
}
while (currentnode != start);
start = prevnode;
return start;
}
struct node* search(struct node* start)
{
struct node *ptr;
ptr=start;
int i=1;
int val;
printf("Enter the value you want to search in the linked list: \n");
scanf("%d",&val)
while(ptr->next!=start)
{ if(ptr->data==val)
{
printf("The element %d is present at %d position in the linked list.\n",val,i);
}
i++;
ptr=ptr->next;
}
if(ptr->data==val)
{
printf("The element %d is present at %d position in the linked list.\n",val,i);
}
}