Write an algorithm for the implementation of a Circularly Doubly Linked List

 

#include<stdio.h> /* Structure declaration */ struct LinkedList { struct LinkedList *previous; int number; struct LinkedList *next; }; typedef struct LinkedList NODE; /* Global variable declaration */ NODE *head, *temp, *p; /* Global functions declaration */ void insertNode(int n); void deleteNode(int n); void displayList(); /* main( ) function */ void main() { int choice, num; while(1) { printf("\n Press 1 for insert number"); printf("\n Press 2 for delete number"); printf("\n Press 3 for display list"); printf("\n Press 4 for exit"); printf("\n Enter your choice : "); scanf("%d",&choice); switch(choice) { case 1: printf("\n Enter the number : "); scanf("%d",&num); insertNode(num); break; case 2: if(head == NULL) printf("\n List is blank !"); else { printf("\n Enter the number : "); scanf("%d",&num); deleteNode(num); } break; case 3: displayList(); break; case 4: exit(0); default: printf("\n\n\n Wrong Input"); } } } /* Insert number into the list */ void insertNode(int n) { /* Check whether the list is blank or not */ /* If blank then create a memory into head variable and place the number into it */ if(head == NULL) { head = (NODE *) malloc(sizeof(NODE)); head->number = n; head->previous = head; head->next = head; } else { /* If the list is not blank then create a memory into temp variable, place the number into it and add this memory to the end of the list */ temp = (NODE *) malloc(sizeof(NODE)); temp->number = n; p = head; while(p->next != head) p = p->next; p->next = temp; temp->previous = p; temp->next = head; head->previous = temp; } } /* Delete a particular number from the list */ void deleteNode(int n) { int found = 0; /* Check whether the list contain only one element or not */ if(head->next == head && head->previous == head) { if(head->number == n) { found = 1; head = NULL; } } else /* Check whether the number found into the first-memory (head) of the list or not ? */ if(head->number == n) { temp = head; head = head->next; head->previous = temp->previous; temp->previous->next = head; found = 1; } else { p = head->next; while(p != head) { if(p->number == n) { p->next->previous = p->previous; p->previous->next = p->next; found = 1; break; } p = p->next; } } if(found == 0) printf("\n Element not found !"); } /* Display list elements */ void displayList() { /* Check whether the list is blank or not */ if(head == NULL) printf("\n List is blank !"); else { p = head; while(p->next != head) { printf("\t%d",p->number); p = p->next; } printf("\t%d",p->number); } }