Circular LinkList

A circular linked list is a Linear Linklist whose last node point back to the head node.

---

#include <stdio.h>

#include <conio.h>

  typedef struct Clist

      {

           int n;

           struct Clist *next;

      }node;

      node *head;

  void Insert(int num)

      {

           node *pr,*temp;

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

           temp->n = num;

           if(head == NULL)

              {

                   head = temp;

                   temp->next = head;

              }

           else

              {

                   temp->next = head->next;

                   head->next = temp;

                   head = temp;

              }

      }

  void InsertBeg(int num)

      {

           node *temp;

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

           temp->n=num;

           temp->next=head->next;

           head->next=temp;

      }

  void InsetAft(int num,int pos)

      {

           node *temp,*pr;

           int i=0;

           pr=head->next;

           while(pr!=NULL)

              {

                   pr=pr->next;

                   if(pr==head->next)

                        {

                            printf("\n\tPosition %d is Out of Range!!",pos);

                            return;

                        }

                   i++;

                   if(i==pos)

                        {

                            break;

                        }

              }

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

           temp->next = pr->next;

           temp->n = num;

           pr->next = temp;

           if(pr==head)

              {

                   head=temp;

              }

      }

  void del(int num)

      {

           node *temp,*pr;

           if( head->next == head && head->n == num)

              {

                   temp = head;

                   head = NULL;

                   free(temp);

                   return;

              }

           pr = head->next;

           if(pr->n == num)

              {

                   temp = pr;

                   head->next = pr->next;

                   free(temp);

                   return;

              }

           while(pr->next != head)

              {

                   if(pr->next->n == num)

                        {

                            temp = pr->next;

                            pr->next = temp->next;

                            free(temp);

                            printf("\n\tThe No. %d is Deleted\n",num);

                            return;

                        }

                   pr = pr->next;

              }

           if(pr->next->n == num)

              {

                   temp = pr->next;

                   pr->next = head->next;

                   free(temp);

                   head = pr;

                   return;

              }

           printf("\n\t %d is Not Present\n",num);

           getch();

      }

  void Disp()

      {

           node *pr;

           if(head == NULL)

              {

                   printf("\n\tList is Undeflow");

                   return;

              }

           pr = head->next;

           printf("\n\tValues in the List : ");

           while(pr != head)

              {

                   printf("%d - ", pr->n);

                   pr = pr->next;

              }

           printf("%d\n",head->n);

           getch();

      }

  void main()

      {

           int ch=0,num,pos;

           head=NULL;

           while(ch!=6)

              {

                   clrscr();

                   printf("\n\t1. Insert");

                   printf("\n\t2. Display");

                   printf("\n\t3. Insert at Begining");

                   printf("\n\t4. Insert After");

                   printf("\n\t5. Delete");

                   printf("\n\t6. Exit");

                   printf("\n\tEnter Choice : ");

                   scanf("%d",&ch);

                   switch(ch)

                        {

                            case 1:

                                printf("\n\tEnter an Element : ");

                                scanf("%d",&num);

                                Insert(num);

                                break;

                            case 2:

                                if(head == NULL)

                                      {

                                                printf("\n\tList is Empty!\n");

                                                getch();

                                       }

                                else

                                      {

                                                Disp();

                                      }

                                                break;

                            case 3:

                                printf("\n\tEnter an Element : ");

                                scanf("%d",&num);

                                InsertBeg(num);

                                break;

                            case 4:

                                printf("\n\tEnter an Element : ");

                                scanf("%d",&num);

                                printf("\n\tEnter the Position of Insertion : ");

                                scanf("%d",&pos);

                                InsetAft(num,pos);

                                break;

                            case 5:

                                if(head == NULL)

                                      {

                                                printf("\n\tUnderflow Condition Occured\n");

                                                getch();

                                      }

                                else

                                      {

                                                printf("\n\tEnter the Number to Delete : ");

                                                scanf("%d",&num);

                                                del(num);

                                      }

                                                break;

                            case 6:

                                printf("\n\tQuit..........");

                                getch();

                                exit(0);

                            default:

                                printf("\n\tThe Choice is Out of Rangen");

                        }

              }

      }