C示例程序更新循环链接列表中的项目

#include <stdio.h>

#include <stdlib.h>



struct node {

   int data;

   struct node *next;

};



struct node *head = NULL;

struct node *current = NULL;



//insert link at the first location

void insert(int data) {

   // Allocate memory for new node;

   struct node *link = (struct node*) malloc(sizeof(struct node));



   link->data = data;

   link->next = NULL;



   // If head is empty, create new list

   if(head==NULL) {

      head = link;

      head->next = link;

      return;

   }



   current = head;



   // move to the end of the list

   while(current->next != head)

      current = current->next;



   // Insert link at the end of the list

   current->next = link;



   // Link the last node back to head

   link->next = head;



}



void update_data(int old, int new) {

   int pos = 0;



   if(head==NULL) {

      printf("Linked List not initialized");

      return;

   }



   current = head;



   while(current->next!=head) {

      if(current->data == old) {

         current->data = new;

         printf("\n%d found at position %d, replaced with %d\n", old, pos, new);

         return;

      }

      current = current->next;

      pos++;

   }



   if(current->data == old) {

      current->data = new;

      printf("\n%d found at position %d, replaced with %d\n", old, pos, new);

      return;

   }      



   printf("%d does not exist in the list\n", old);

}



//display the list

void printList() {

   struct node *ptr = head;



   printf("\n[head] =>");



   //start from the beginning

   while(ptr->next != head) {        

      printf(" %d =>",ptr->data);

      ptr = ptr->next;

   }



   printf(" %d =>",ptr->data);

   printf(" [head]\n");

}



int main() {

   insert(10);

   insert(20);

   insert(30);

   insert(1);

   insert(40);

   insert(56);



   printList();

   update_data(56,11);

   printList();



   return 0;

}