数据结构链表

#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;



//display the list

void printList() {

   struct node *ptr = head;

   printf("\n[ ");



   //start from the beginning

   while(ptr != NULL) {

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

      ptr = ptr->next;

   }



   printf(" ]");

}



//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;



   //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;



   //mark next to first link as first

   head = head->next;



   //return the deleted link

   return tempLink;

}



//is list empty

bool isEmpty() {

   return head == NULL;

}



int length() {

   int length = 0;

   struct node *current;



   for(current = head; current != NULL; current = current->next) {

      length++;

   }



   return length;

}



//find a link with given key

struct node* find(int key) {



   //start from the first link

   struct node* current = head;



   //if list is empty

   if(head == NULL) {

      return NULL;

   }



   //navigate through list

   while(current->key != key) {



      //if it is last node

      if(current->next == NULL) {

         return NULL;

      } else {

         //go to next link

         current = current->next;

      }

   }      



   //if data found, return the current Link

   return current;

}



//delete a link with given key

struct node* delete(int key) {



   //start from the first link

   struct node* current = head;

   struct node* previous = NULL;



   //if list is empty

   if(head == NULL) {

      return NULL;

   }



   //navigate through list

   while(current->key != key) {



      //if it is last node

      if(current->next == NULL) {

         return NULL;

      } else {

         //store reference to current link

         previous = current;

         //move to next link

         current = current->next;

      }

   }



   //found a match, update the link

   if(current == head) {

      //change first to point to next link

      head = head->next;

   } else {

      //bypass the current link

      previous->next = current->next;

   }    



   return current;

}



void sort() {



   int i, j, k, tempKey, tempData;

   struct node *current;

   struct node *next;



   int size = length();

   k = size ;



   for ( i = 0 ; i < size - 1 ; i++, k-- ) {

      current = head;

      next = head->next;



      for ( j = 1 ; j < k ; j++ ) {   



         if ( current->data > next->data ) {

            tempData = current->data;

            current->data = next->data;

            next->data = tempData;



            tempKey = current->key;

            current->key = next->key;

            next->key = tempKey;

         }



         current = current->next;

         next = next->next;

      }

   }   

}



void reverse(struct node** head_ref) {

   struct node* prev   = NULL;

   struct node* current = *head_ref;

   struct node* next;



   while (current != NULL) {

      next  = current->next;

      current->next = prev;   

      prev = current;

      current = next;

   }



   *head_ref = prev;

}



void 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();

   insertFirst(1,10);

   insertFirst(2,20);

   insertFirst(3,30);

   insertFirst(4,1);

   insertFirst(5,40);

   insertFirst(6,56);



   printf("\nRestored List: ");

   printList();

   printf("\n");  



   struct node *foundLink = find(4);



   if(foundLink != NULL) {

      printf("Element found: ");

      printf("(%d,%d) ",foundLink->key,foundLink->data);

      printf("\n");  

   } else {

      printf("Element not found.");

   }



   delete(4);

   printf("List after deleting an item: ");

   printList();

   printf("\n");

   foundLink = find(4);



   if(foundLink != NULL) {

      printf("Element found: ");

      printf("(%d,%d) ",foundLink->key,foundLink->data);

      printf("\n");

   } else {

      printf("Element not found.");

   }



   printf("\n");

   sort();



   printf("List after sorting the data: ");

   printList();



   reverse(&head);

   printf("\nList after reversing the data: ");

   printList();

}