C示例组合两个双向链表

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C示例组合两个双向链表

#include <stdio.h>

#include <stdlib.h>



struct node {

   int data;

   struct node *prev;

   struct node *next;

};



struct node *list = NULL;

struct node *list_last = NULL;



struct node *even = NULL;

struct node *even_last = NULL;



struct node *odd = NULL;

struct node *odd_last = NULL;



struct node *current = NULL;



//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(data%2 == 0) {

      if(even == NULL) {

         even = link;

         return;

      } else {

         current = even;



         while(current->next != NULL)

            current = current->next;



         // Insert link at the end of the list

         current->next = link;

         even_last = link;

         link->prev = current;

      }

   } else {

      if(odd == NULL) {

         odd = link;

         return;

      } else {

         current = odd;



         while(current->next!=NULL)

            current = current->next;



         // Insert link at the end of the list

         current->next = link;

         odd_last = link;

         link->prev = current;

      }

   }

}



//display the list

void print_backward(struct node *head) {

   struct node *ptr = head;



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

   //start from the beginning

   while(ptr != NULL) {        

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

      ptr = ptr->prev;

   }



   printf(" [head]\n");

}



//display the list

void printList(struct node *head) {

   struct node *ptr = head;



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

   //start from the beginning

   while(ptr != NULL) {        

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

      ptr = ptr->next;

   }



   printf(" [last]\n");

}



void combine() {

   struct node *link;



   list = even;

   link = list;



   while(link->next!= NULL) {

      link = link->next;

   }



   link->next = odd;

   odd->prev = link;



   // assign link_last to last node of new list



   while(link->next!= NULL) {

      link = link->next;

   }



   list_last = link;  

}



int main() {

   int i;



   for(i = 1; i <= 10; i++)

      insert(i);



   printf("Even : ");

   printList(even);



   printf("Even (R): ");

   print_backward(even_last);



   printf("Odd  : ");

   printList(odd);



   printf("Odd (R) : ");

   print_backward(odd_last);



   combine();



   printf("Combined List :\n");

   printList(list);



   printf("Combined List (R):\n");

   print_backward(list_last);



   return 0;

}