单向链表例题



#include <stdio.h>
#include <stdlib.h>

struct node        //定义结点的结构体
{
 int num;
 char name[100];

 struct node *next;
};

typedef struct node Node;    //将struct node简单定义为Node
typedef struct node *Link;    //将stcuct node类型定义为*Link

void create_link(Link * head)   //创建头指针，并定义为空指针
{
 *head = NULL;
}

void insert_node_head(Link * head, Link new_node) //插入新的结点（头插）（插哪，哪个结点)
{
 new_node -> next = *head;
 *head = new_node;
}

void insert_node_tail (Link * head, Link new_node)   //尾插
{
 Link p = NULL;
    p = *head;

 if(p == NULL)            //链表为空
 {
        *head = new_node;
  new_node -> next = NULL;
 }
 else
 {
  while(p -> next != NULL)
  {
   p = p -> next;  
  }

  p -> next = new_node;
  new_node -> next = NULL;
 }
}

void display_link (Link head)        //输出
{
 Link p ;
 p = head;

 if(head == NULL)
 {
  printf("Link is empty!\n");
  return;
 }

 while(p != NULL)
 {
  printf("num = %d\n",p -> num);
  printf("name = %s\n",p -> name);
  printf("\n");
  p = p -> next;     //下一个
 }
}

void release_link (Link * head)             //释放链表
{
 Link p;
 p = *head;
   
    while(*head != NULL)
 {
        p = *head;
  *head = (*head) -> next;
     free(p);
 }

}

void delete_node (Link * head, int number)      //删除其中一个结点
{
    Link p = NULL;
 Link q = NULL;
 p = * head;
 q = * head;

 if(*head == NULL)
 {
  return;
 }
 else
 {
  if((*head) -> num == number)
  {
   *head = p -> next;
   free(p);
  }
  else
  {
   while(p != NULL && p -> num != number)
   {
    q = p;
    p = p -> next;
   }

   if(p == NULL)
   {
    printf("no node!\n");
   }
   else if( p->next != NULL)
   {
    q -> next = p -> next;
    free(p);
   }
   else
   {
       q -> next = NULL;
    free(p);
   }
  }
 }
}

int number_link (Link head)         //计算链表长度并返回
{
 Link p;
 p = head;
 int num = 0;

 while(p != NULL)
 {
  p = p -> next;
  num++;
 }

 return num;

}

Link find_link (Link  head, int n)        //查找对应学号所在结点内容
{
 Link p;
 p = head;

 while(p -> num != n && p != NULL)
 {
  p = p -> next;
 }

 return p;
}

void flashback_link (Link *head)       //倒叙输出链表
{
 Link p1;
 Link p2;
 Link p3;

 p1 = *head;
 p2 = p1 -> next;
 p3 = p2 -> next;

 if(*head == NULL || p1 -> next == NULL)
 {
        return;
 }
 else if(p2 -> next == NULL)
 {
  p2 -> next = p1;
  p1 -> next = NULL;
  *head = p2;
 }
 else
 {
  p2 -> next = p1;

  while(p3 -> next != NULL)
  {
   p1 = p2;
   p2 = p3;
   p3 = p3 -> next;
   p2 -> next = p1;
  }
  p3 -> next = p2;
  (*head) -> next = NULL;
  *head = p3;
 }
}

void enter_link (Link *head, Link enter_node,int number)   //插入新的结点
{
    Link p = NULL;
 p = * head;
   
 if(*head == NULL)    //空
 {
  *head = enter_node;
  enter_node -> next = NULL;
 }
 else if(p -> num == number)
 {
  enter_node -> next = *head;
  *head = enter_node;
 }
 else
 {
  while(p != NULL && p -> num != number)
  {
   p = p -> next;
  }
  
  if(p != NULL)
  {
   p = *head;
   while((p->next) -> num != number)
   {
    p = p -> next;
   }
   (enter_node) -> next = (p -> next);
   p -> next = enter_node;
  }
  else
  {
   p = *head;
      while(p -> next != NULL)
   {
    p = p -> next;
   }
   p -> next = enter_node;
   enter_node -> next = NULL;
  }

 }

}

int main()
{
 Link head = NULL;
 Link new_node = NULL;
 Link enter_node = NULL;
 int i;
 int n;
 int num;
 int number;

 create_link(&head);

 for(i = 0; i < 3; i++)
 {
  new_node = (Link)malloc(sizeof( Node ));   //创建一个新的结点

  if(new_node == NULL)    //检查分配空间
  {
   printf("malloc error!\n");
   exit(-1);
  }

  new_node -> num = i + 1;  //赋值
  scanf("%s", new_node -> name);

  //      insert_node_head(&head, new_node)；
  insert_node_tail(&head, new_node);
 }

// display_link(head); //输出
/*
 num = number_link(head);               //返回结点数
 printf("number = %d\n", num);

 printf("Please input the num, find the name:\n");
 scanf("%d",&n);
 printf("%s\n",find_link(head, n) -> name);           // 输出查找号对应的名字
 printf("\n");

 printf("Please input the number of delete:\n");
 scanf("%d",&number);
    delete_node (&head, number);       //删除其中一个结点

 flashback_link(&head);      //倒叙输出
*/ 

 enter_node = (Link)malloc(sizeof(Node));
 enter_node -> num = i + 1;
 printf("Please input the name:\n");
 scanf("%s",enter_node -> name);
 printf("Please input the number of enter:\n");
 scanf("%d",&number);
 enter_link(&head, enter_node, number);    //在已经输入的结点里再插入一个新的结点

 display_link(head); //输出

 release_link (&head); //释放
   
 display_link(head);

    return 0;
}