查找链接列表的大小（Find size of Linked List）

实现 (Implementation)

该算法的实现如下 -

#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;
}

输出 (Output)

该方案的产出应该是 -

[head] <=> 10 <=> 20 <=> 30 <=> 1 <=> 40 <=> 56 <=> [last]
56 found at position 6