Programme de listes liées circulaires en C

La liste liée circulaire est une variante de la liste liée dans laquelle le premier élément pointe vers le dernier élément et le dernier élément pointe vers le premier élément. La liste à liaison unique et la liste à liaison double peuvent être transformées en une liste liée circulaire.

Implémentation en C

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>

struct node {
   int data;
   int key;
	
   struct node *next;
};

struct node *head = NULL;
struct node *current = NULL;

bool isEmpty() {
   return head == NULL;
}

int length() {
   int length = 0;

   //if list is empty
   if(head == NULL) {
      return 0;
   }

   current = head->next;

   while(current != head) {
      length++;
      current = current->next;   
   }
	
   return length;
}

//insert link at the first location
void insertFirst(int key, int data) {

   //create a link
   struct node *link = (struct node*) malloc(sizeof(struct node));
   link->key = key;
   link->data = data;
	
   if (isEmpty()) {
      head = link;
      head->next = head;
   } else {
      //point it to old first node
      link->next = head;
		
      //point first to new first node
      head = link;
   }    
}

//delete first item
struct node * deleteFirst() {

   //save reference to first link
   struct node *tempLink = head;
	
   if(head->next == head) {  
      head = NULL;
      return tempLink;
   }     

   //mark next to first link as first 
   head = head->next;
	
   //return the deleted link
   return tempLink;
}

//display the list
void printList() {

   struct node *ptr = head;
   printf("\n[ ");
	
   //start from the beginning
   if(head != NULL) {
	
      while(ptr->next != ptr) {     
         printf("(%d,%d) ",ptr->key,ptr->data);
         ptr = ptr->next;
      }
   }
	
   printf(" ]");
}

void main() {
   insertFirst(1,10);
   insertFirst(2,20);
   insertFirst(3,30);
   insertFirst(4,1);
   insertFirst(5,40);
   insertFirst(6,56); 

   printf("Original List: "); 
	
   //print list
   printList();

   while(!isEmpty()) {            
      struct node *temp = deleteFirst();
      printf("\nDeleted value:");  
      printf("(%d,%d) ",temp->key,temp->data);
   }   
	
   printf("\nList after deleting all items: ");
   printList();   
}

Si nous compilons et exécutons le programme ci-dessus, il produira le résultat suivant -

Production

Original List: 
[ (6,56) (5,40) (4,1) (3,30) (2,20) ]
Deleted value:(6,56) 
Deleted value:(5,40) 
Deleted value:(4,1) 
Deleted value:(3,30) 
Deleted value:(2,20) 
Deleted value:(1,10) 
List after deleting all items: 
[ ]