迴圈連結串列範例程式（C語言）

使用 C語言來實現迴圈連結串列的範例程式，如下所示：

#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(" ]");
}

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();   
}

如果我們編譯並執行上述程式那麼這將產生以下結果 -

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: 
[ ]