C语言链表问题。急！！！

题目是这样的：
（等看到答案再加分）
  1 建立一个数据域长度不超过n的字符串的单链表
  2 将一指定字符串插入到单链表的指定位置，不允许重复
  3 将单链表中一指定字符串删除
 

答案：#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int n;
typedef struct node
{
     char string[80];
     struct node *next;
}link;
link *creat()
{
link *head,*p1,*p2;
p1=p2=(link *)malloc(sizeof(link));
gets(p1->string);
while(p1->string[0]!='0')
{
n++;
if(n==1) head=p1;
else p2->next=p1;
p2=p1;
p1=(link *)malloc(sizeof(link));
gets(p1->string);
}
p2->next=NULL;
free(p1);
return head;
}
link *ins(link *head,char *str,int i)
{
if(i>n)
return head;
link *p1,*p2,*p0;
int h;
p1=head;h=0;
while(h<i)
{p2=p1;p1=p1->next;h++}
p0=(link *)malloc(sizeof(link));
strcpy(p0->string,str);
p0->next=p1;
p2->next=p0;
return head;
}
link *del(link *head,char *str)
{
link *p1,*p2;
p1=head;
while(strcmp(p1->string,str)&&p1->next)
{p2=p1;p1=p1->next}
if(p1->next)
{p2->next=p1->next;free(p1)}
else printf("%s not found!\n",str);
return head;
}
main函数我不写了。。。
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
#include<string.h>
int ig;                                                                  /*定义全局变量*/
struct link                                                              /*结构体指针*/
{
 char str[20];                                                     /*定义数据域*/
 struct link *next;                                               /*指针域    */
};
struct link *create(void)                                                /*创建      */
{ struct link *head=NULL,*new,*tail;
  int icount=0;                                                    /*计数器初始化*/
  while(1)
  {  new=(struct link *)malloc(sizeof(struct link));
    printf("input the string(-1 to end) No. %d:",icount+1);
    scanf("%s",new->str);
    if(strcmp(new->str,"-1")==0)                             /*输入-1时结束*/
    {  new=NULL;
      free(new);                                       /*释放new   */
      return head;                                     /*结束输入  */
    }
    else
    {  icount++;                                        /*计数      */
      if(icount==1)                                    /*第一个结点*/
      {  head=tail=new;
      }
      else
      {  tail->next=new;
        tail=new;                                /*以后的所有结点*/
      }
    }
  }
}
struct link *add(struct link *head,int ik,char ckey[20])                               /*添加结点    */
{  struct link *p,*new;
  int ij;
  new=(struct link *)malloc(sizeof(struct link));                  /*新结点分配内存*/
  strcpy(new->str,ckey);
  new->next=NULL;                                          /*设置当前指针域*/
  if(head==NULL)
    head=new;
  else
  {  if(ik==0)                                        /*新结点在head后*/
      new->next=head,head=new;
    else
    {  p=head,ij=0;
      while(p->next!=0&&ij<ik-1)
      {  p=p->next,ij++;                  /*新结点在链表中部*/
      }
      new->next=p->next,p->next=new;
    }
    return head;
  }
}
struct link *delete(struct link *head,int ikey)                          /*删除函数     */
{  struct link *p,*q;
 

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