合并两个链表，为什么第二次输入链表后输出的是空表？是不是第二次调用ininlise后有那个内存释放问题？新手不懂，各位大哥来个提示吧。。呵呵，谢谢。。。
#include<stdio.h>
#include<malloc.h>
#define len sizeof(struct list)
#define null 0
struct list

{
  int num;
  struct list *next;
};
int n=0;
struct list *initlist(void)
{
  struct list *p1,*p2,*head;
  p1=p2=(struct list*)malloc(len);
  head=null;
  printf(" qing shu ru:");
  scanf("%d",&p1->num);
  while(p1->num!=0)
  {
      n++;
      if (n==1)
    head=p1;
    else
    {
      p2->next=p1;
      p2=p1;
      p1=(struct list*)malloc(len);
      printf("qing shu ru:");
      scanf("%d",&p1->num);
    }
    p2->next=null;
  }
  return head;
}

void print(struct list *head)
{
  struct list *p;
  p=head;
  if (p==null)
    printf("空表");
  else
      while(p!=0)
      {
    printf("num is :%d",p->num);
      p=p->next;
      }
}
struct list *L(struct list *l1,struct list *l2)
{
    struct list *p1,*p2,*p3,*head;
    p1=l1,p2=l2;
    p3=l1;
    head=p3;
    while(p1!=0&&p2!=0)
    {
        if(p1->num<p2->num)
        {
        p3->next=p1;
        p1=p1->next;
        }
        else
        {
            p3->next=p2;
            p2=p2->next;
        }
    }
    if(p1!=0)
    {
    p3->next=p2;
    }
    else
    {
        p3->next=p1;
    }
}
void main()
{
    struct list *l1,*l2,*l3;
    l1=initlist();
    print(l1);
    l2=initlist();
    print(l2);
    l3=L(l1,l2);
    print(l3);
}

#include<stdio.h>
#include<malloc.h>
#define len sizeof(struct list)
#define NULL 0//---------------------------用NULL
struct list
{
  int num;
  struct list *next;
};
int n=0;
struct list *initlist(void)
{
  struct list *p1,*p2,*head;
  p1=p2=(struct list*)malloc(len);
  head=0;//-------------------------------修改
  printf(" qing shu ru:");
  scanf("%d",&p1->num);
  while(p1->num!=0)
  {
      n++;
      if (n==1)
    head=p1;
    else
    {
      p2->next=p1;
      p2=p1;
      p1=(struct list*)malloc(len);
      printf("qing shu ru:");
      scanf("%d",&p1->num);
    }
    p2->next=0;//-------------------------------修改
  }
  return head;
}

void print(struct list *head)
{
  struct list *p;
  p=head;
  if (p==0)//-------------------------------修改
    printf("空表");
  else
      while(p!=0)
      {
    printf("num is :%d",p->num);
      p=p->next;
      }
}
struct list *L(struct list *l1,struct list *l2)
{
    struct list *p1,*p2,*p3,*head;
    p1=l1,p2=l2;
    p3=l1;
    head=p3;
    while(p1!=0&&p2!=0)
    {
        if(p1->num<p2->num)
        {
        p3->next=p1;
        p1=p1->next;
        }
        else
        {
            p3->next=p2;
            p2=p2->next;
        }
    }
    if(p1!=0)
    {
    p3->next=p2;
    }
    else
    {
        p3->next=p1;
    }
}
main()
{
    struct list *l1,*l2,*l3;
    l1=initlist();
    print(l1);
    l2=initlist();
    print(l2);
    l3=L(l1,l2);
    print(l3);
}

主要是C中要区分大小写，并没有null语句，只有NULL

呵呵，感谢回答。但是我做插入删除什么的都用小写的宏啊，都可以的啊