C示例程序搜索双链表

#include <stdio.h>

#include <stdlib.h>



struct node {

   int data;

   struct node *prev;

   struct node *next;

};



struct node *head = NULL;

struct node *last = NULL;



struct node *current = NULL;



//display the list

void printList() {

   struct node *ptr = head;



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

   //start from the beginning

   while(ptr != NULL) {        

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

      ptr = ptr->next;

   }



   printf(" [last]\n");

}



//Create Linked List

void insert(int data) {

   // Allocate memory for new node;

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



   link->data = data;

   link->prev = NULL;

   link->next = NULL;



   // If head is empty, create new list

   if(head==NULL) {

      head = link;

      return;

   }



   current = head;



   // move to the end of the list

   while(current->next!=NULL)

      current = current->next;



   // Insert link at the end of the list

   current->next = link;

   last = link;

   link->prev = current;

}



void search(int data) {

   int pos = 0;



   if(head==NULL) {

      printf("Linked List not initialized");

      return;

   }



   current = head;

   while(current!=NULL) {

      pos++;

      if(current->data == data) {

         printf("%d found at position %d\n", data, pos);

         return;

      }



      if(current->next != NULL)

         current = current->next;

      else

         break;

   }



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

}



int main() {

   insert(10);

   insert(20);

   insert(30);

   insert(1);

   insert(40);

   insert(56);



   printList();

   search(56);



   return 0;

}