循环链表

#include "stdafx.h"
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

struct node{
   char c;
   struct node *next;
};
typedef struct node *Link;

Link init(Link head){
   Link before;
   Link newnode;
   Link tail;

   int i, num;
   char str[101];
   scanf("%s",str);
   num = strlen(str);

   head->c = str[0];
   head->next = NULL;
   before = head;
   for(i=1;i<num;i++){
      newnode = (Link)malloc(sizeof(struct node));
      if(!newnode)
         return NULL;
      newnode->c = str[i];
      newnode->next = NULL;
      before->next = newnode;
      before = newnode;
   }
   newnode->next = head;
   tail = newnode;
   return tail;
}

void Insert(Link* hd,Link *tl,char ch){
   Link s,p,q;
   p = *hd;
   q = *tl;
   s = (Link)malloc(sizeof(struct node));\
   s->c = ch;

   s->next = p;
   q->next = s;
   q = q->next;
   *tl=q;
}

void Delete(Link *hd,Link *tl){
   Link p,q,r;
   p = *hd;
   r = p;
   q = *tl;
   p = p->next;
   q->next = p;
   free(r);
   *hd = p;
   *tl = q;
}
void print(Link *hd, Link *tl){
   Link p,q;
   p = *tl;
   q = *tl;
   do{
      printf("%c",q->c);
      q = q->next;
   }while(p!=q);
}

int _tmain(int argc, _TCHAR* argv[])
{
   char ch;
   int i;
   int playnum;
   int choose;
   Link head;
   Link tail;
   Link tmp;
   head = (Link)malloc(sizeof(struct node));
   freopen("linklist_i.txt","r",stdin);
   freopen("linklist_o.txt","w",stdout);
   setbuf(stdout,NULL);
   scanf("%d", &playnum);
   tail=init(head);

   for(i=0;i<playnum;i++){
      scanf("%d", &choose);
      if(choose==1){
         scanf(" %c",&ch);
         Insert(&head, &tail, ch);
      }else if(choose==2){
         if(!(tail->next==tail)){
            Delete(&head, &tail);
         }

      }else if(choose==3){
         tail = head;
         head = head->next;
      }
   }

   print(&head, &tail);
   printf("\n");
   while(head!=tail)
   {
      tmp=head;
      head=head->next;
      free(tmp);
   }
   return 0;
}

/************************************************************************\
学校有个神奇的机器,他里面的数据呈环状排列.机器有以下操作
1. 往操作位置顺时针的下一位插入一个元素,并将操作位置移到新元素上.
2. 删掉操作位置顺时针方向的下一位.如果没有数据,不做操作.
3. 使得操作位置顺时针移动一位.
现在机器中有一组长度不超过100的字符串数据,我们希望知道对这些数据进行n次操
作以后的序列情况.(第一次操作从现存数据的最后一位开始)
\************************************************************************/

/* Input
6 操作次数
adc 初始字符串
1 a 下面是6次操作
2
2
3
1 m
3
*/
/* Output
acm
*/