C语言之单循环链表

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#include<stdio.h>
#include<stdlib.h>
struct node
{
         int data;
         struct node *next;
};
struct node *Init(struct node *head);
void Print_list(struct node *head);
struct node *insert(struct node *head,int i);
struct node *Delete(struct node *head,int i);

struct node *Delete(struct node *head,int i)
{
         struct node *t,*s;
         struct node *pr=head;
         int j;
         if(i==1)
         { 
          for(t=pr;t->next!=pr;t=t->next);                            //找尾指针 //找到最后一个节点
          s=pr;                                                                       //删除第一个节点意味着连接第二个节点
          pr=pr->next;                                                         //找到指向第二个节点的指针
          t->next=pr;
          free(s);
          return pr;                                                                  //删除第一个节点
 }    
 else
 {
          t=pr;
          for(j=1;j<i;j++)                                                       //找到要删除的位置的前一个指针
          {                                                                            //连接删除位置后一个节点
           t=t->next;         
          }
          s=t->next;
          t->next=s->next;
          return pr;
     }
}

struct node *insert(struct node *head,int i)
{
         int item;
         int j;
         struct node *s,*t;
         struct node *pr=head;               //第一步：用一个指针pr代替传入的head指针 用pr来操作链表
                                                             //第二步：判断传入的链表是否为空
                                                             //第三步：为空 结束 无法插入；不为空，插入（循环的插入逻辑很简单）
        printf("输入要插入的值\n");
         scanf("%d",&item);
         if(i==1)
          {
                  s=(struct node *)malloc(sizeof(struct node));                //创建一个节点s 
                  if(s==NULL)
                      {
                           printf("创建失败\n");
                           exit(0);
                      }   
                   s->data=item;       
                   s->next=pr->next;      
                   pr->next=s;        
                   return pr;
 }
 else
 {
          t=pr;
          for(j=1;j<i;j++)
          {
               t=t->next;                                        //遍历到要插入的位置，一般来说用循环次数来结束遍历到了第几个位置
          }
          s=(struct node *)malloc(sizeof(struct node));
          if(s==NULL)
          {
                   printf("创建失败\n");
                   exit(0);
          }
          s->data=item;
          s->next=t->next;
          t->next=s;
          return pr;
     }
}
void Print_list(struct node *head)
{
             struct node *p;
             for(p=head->next;p!=head;p=p->next)
             {
              printf("%d ",p->data);
             }
             printf("\n");
            }

struct node *Init(struct node *head)
    {
         int item;
         struct node *t;
         struct node *s;    
         struct node *pr=head;                           //第一步：用一个指针pr代替传入的head指针 用pr来操作链表
                                                              //第二步：判断传入的链表是否为空
                                                           //第三步：为空 一种初始化方式；不为空，另一种初始化方式（循环的创建逻辑很简单）
         while(1)
         {
              printf("输入节点的值\n");
              scanf("%d",&item);
              fflush(stdin);
              if(pr==NULL)                       //判断为空表之后的操作
              {
                   pr=(struct node *)malloc(sizeof(struct node));     //创建一个头结点，然后使头尾相接
                   if(pr==NULL)
                       {
                            printf("创建失败\n");
                            exit(0);
                       }            
                  pr->next=pr;           //头尾相接的操作
                  return  pr;         
              }      
              else     //如果不是空表 之后的操作        不是空表，自带头结点
              {
                   for(t=pr;t->next!=pr;t=t->next);                                //用个循环找到尾结点，后面需要用尾结点操作  
                   s=(struct node *)malloc(sizeof(struct node));             //创建一个节点  插入到头节点和尾结点之间
                   if(s==NULL)
                       {
                            printf("创建失败\n");
                            exit(0);
                       }
                       s->data=item;
                       s->next=pr;
                       t->next=s;  //将s新节点插入到头结点和尾节点之间的操作
                       return  pr; 
              }
         }
        }
            int main()
            {
                 struct node *head=NULL;
                 int n,i;
                 while(n!=0)
             {
                  printf("单循环链表的基本操作\n");
                  printf("-----------------------------");
                  printf("1.创建一个节点\n");
                  printf("2.插入节点\n");
                  printf("3.删除节点\n");
                  printf("4.显示链表成员\n");
                  printf("0.退出\n");
                  printf("请选择操作\n");
                  scanf("%d",&n);
                  switch(n)
                  {
                       case 1:
                        {
                             head=Init(head);
                             break;
                        }
                       case 2:
                        {
                             printf("插入的位置是\n");
                             scanf("%d",&i);
                             head=insert(head,i);
                             break;
                        }
                       case 3:
                        {
                             printf("删除的位置是\n");
                             scanf("%d",&i);
                             head=Delete(head,i);
                             break;
                        }
                       case 4:
                        {
                             Print_list(head);
                             break;
                        }
                  }
             }
 return 0;
    }