#include "stdio.h"
#include "conio.h"
#define NULL 0
#define LEN sizeof(struct student)

struct student
{char num[6];
 char name[8];
 struct student *next;
};

struct student *creat(void)
{struct student *p1,*p2,*head;
 int n=0;
 p1=p2=(struct student *)malloc(LEN);
 head=NULL;
 printf("Input 0 to end.\n");
 printf("Input num,name:\n");
 scanf("%s,%s",&p1->num,&p1->name);
 while(p1!=NULL)
 {if(n==0)head=p1;
  else p2->next=p1;
  n++;
  p2=p1;
 }
 p2->next=NULL;
 return(head);
}

void print(struct student *p)
{while(p!=NULL)
 {printf("%4s,%4s\n",p->num,p->name);
  p=p->next;
 }
}

main()
{struct student *ha,*hb,*p1,*p2,*p;
 ha=creat();
 hb=creat();
 print(ha);
 print(hb);
 p1=ha;
 p2=hb;
/*delete*/
 while(p1!=NULL)
 {if(strcmp(p2->num,p1->num)!=0)
  p2=p2->next;
  else
  {if(p1==ha)
      p1->next=ha;
   else
      p->next=p1->next;
   p=p1;
   p1=p1->next;                    这里是不是有问题？
  }
 }
 print(ha);
    getch();
}

#include "stdio.h"
#include "conio.h"
#define NULL 0
#define LEN sizeof(struct student)

struct student
{char num[6];
char name[8];
struct student *next;
};

struct student *creat(void)
{struct student *p1,*p2,*head;
int n=0;
p1=p2=(struct student *)malloc(LEN);
head=NULL;
printf("Input 0 to end.\n");
printf("Input num,name:\n");
scanf("%s,%s",&p1->num,&p1->name);
while(p1!=NULL)
{if(n==0)head=p1;
  else p2->next=p1;
  n++;
  p2=p1;
}
p2->next=NULL;
return(head);
}

void print(struct student *p)
{while(p!=NULL)
{printf("%4s,%4s\n",p->num,p->name);
  p=p->next;
}
}

main()
{struct student *ha,*hb,*p1,*p2,*p;
ha=creat();
hb=creat();
print(ha);
print(hb);
p1=ha;
p2=hb;
/*delete*/
while(p1!=NULL)
{if(strcmp(p2->num,p1->num)!=0)
  p2=p2->next;
  else
  {if(p1==ha)
      p1->next=ha;
   else
      p->next=p1->next;
   }
   p=p1;
   p1=p1->next;                    这里是不是有问题？要删除链表A中与B中相同的元素
  }
print(ha);
    getch();
}

#include "stdio.h"
#include "conio.h"
#define NULL 0
#define LEN sizeof(struct student)

struct student
{char num[6];
char name[8];
struct student *next;
};

struct student *creat(void)
{struct student *p1,*p2,*head;
int n=0;
p1=p2=(struct student *)malloc(LEN);
head=NULL;
printf("Input 0 to end.\n");
printf("Input num,name:\n");
scanf("%s,%s",&p1->num,&p1->name);
while(p1!=NULL)
{if(n==0)head=p1;
  else p2->next=p1;
  n++;
  p2=p1;
}
p2->next=NULL;
return(head);
}

void print(struct student *p)
{while(p!=NULL)
{printf("%4s,%4s\n",p->num,p->name);
  p=p->next;
}
}

main()
{struct student *ha,*hb,*p1,*p2,*p;
ha=creat();
hb=creat();
print(ha);
print(hb);
p1=ha;
/*delete*/
while(p1!=NULL)
{p2=hb;
 if(strcmp(p2->num,p1->num)!=0)
  p2=p2->next;
  else
  {if(p1==ha)
      p1->next=ha;
   else
      p->next=p1->next;        问题是如果第一次就执行这句程序时，指针p并没有指向任一节点，哪来的p->next?
   }
   p=p1;                        这句程序未执行前。哪来的p->next。
   p1=p1->next;               
  }
print(ha);
    getch();
}

#include "stdio.h"
#include "conio.h"
#define NULL 0
#define LEN sizeof(struct student)

struct student
{char num[6];
char name[8];
struct student *next;
};

struct student *creat(void)
{struct student *p1,*p2,*head;
int n=0;
p1=p2=(struct student *)malloc(LEN);
head=NULL;
printf("Input 0 to end.\n");
printf("Input num,name:\n");
scanf("%s,%s",&p1->num,&p1->name);
while(p1!=NULL)
{if(n==0)head=p1;
  else p2->next=p1;
  n++;
  p2=p1;
}
p2->next=NULL;
return(head);
}

void print(struct student *p)
{while(p!=NULL)
{printf("%4s,%4s\n",p->num,p->name);
  p=p->next;
}
}

main()
{struct student *ha,*hb,*p1,*p2,*p;
ha=creat();
hb=creat();
print(ha);
print(hb);
p1=ha;
/*delete*/
while(p1!=NULL)
{p2=hb;
if(p2!=NULL&&strcmp(p2->num,p1->num)!=0)                   这样改是不是就可以了。
  p2=p2->next;
  else
  {if(p1==ha)
      p1->next=ha;
   else
      p->next=p1->next;        
   }
   p=p1;                        
   p1=p1->next;               
  }
print(ha);
    getch();
}

如果第一次删的是表头，第二次还是删表头，好像程序就有问题了啊。。？

我知道了，实际上也是可以的。。。。。。