大家帮忙看一下为什么会出错？

做的是一个带有头结点的单链表，思路是先在main中定义头结点，然后在create函数中构造首元结点，接着在insert函数中判断输出是否结束（以$作为结束标志）。

#include <stdio.h>
#include <malloc.h>
#define ElemType int
#define OVERFLOW 0
#define OK 1
typedef struct node{
    ElemType data;
    struct node *next;
}list;
int create(list *head){
    list *t;
    t=(list*)malloc(sizeof(list));
    if(!t){
        printf("\n分配空间失败！");
        return (OVERFLOW);
    }
    head = t;
    int x;
    printf("\nenter a number(end with $):");
    scanf("%d",&x);
    if(x!='$'){
        t=(list*)malloc(sizeof(list));
        t->data = x;
        t->next = NULL;
        head->next = t;
    }
    return OK;
}
int insert(list *head){
    list *t,*m,*n;//m和n表示相邻的两个节点，用于与节点比较大小，然后插入 
    int x;
    scanf("%d",&x);
    while(x!='$'){
        t=(list*)malloc(sizeof(list));
        if(!t) return(OVERFLOW);
        t->data = x;
        t->next = NULL;
        m = head->next;//这里调试出现错误 
        n = head; 
        if(t->data <= m->data){ 
            n->next = t;
            t->next = m;
        }
        else{
            while(1){
                m = m->next;
                n = n->next;
                if(t->data<=m->data){
                    n->next = t;
                    t->next = m;
                    break;
                }
                if(m->next==NULL) break;
            }
            if(m->next==NULL)
                m->next = t;
        }
        scanf("%d",x); 
    }
    return (OK);
}
int main(void){
    //创建一个有头结点的链表 
    printf("create a list");
    int i;
    list *head = NULL;
    i = create(head);
    if(i) insert(head);
    return 0; 
} 

然后我把create的返回值类型改成list*，返回head，然后再把main改一下就不出错了，这是为什么呢？
求大神解答，刚入门，轻喷- -
谢谢！

帮你又改了一下：

 #include <stdio.h>
#include <malloc.h>
#define ElemType int
#define OVERFLOW 0
#define OK 1
typedef struct node
{ 
ElemType data; 
struct node *next;
}list;
list* create(list *head)
{
    list *t; 
    t=(list*)malloc(sizeof(list));
    if(!t)
    { 
    printf("\n分配空间失败！"); 
    return (OVERFLOW); 
    }
    head = t; 
    int x; 
    printf("\nenter a number(end with $):"); 
    scanf("%d",&x);
     if(x!='$')
     {
        t=(list*)malloc(sizeof(list)); 
        t->data = x;
        t->next = NULL;
         head->next = t;
     }
     return head;
}
void insert(list *head)
{
    list *t,*m,*n;
//m和n表示相邻的两个节点，用于与节点比较大小，然后插入 
    int x;
    scanf("%d",&x); 
    while(x!=0)
    {
        t=(list*)malloc(sizeof(list)); 
        if(!t)
        return;
        t->data = x; 
        t->next = NULL; 
        m = head->next;
        //这里调试出现错误 
        n = head;
        if(t->data <= m->data)
        {
            n->next = t;
            t->next = m;
        }
        else
        {
            while(1)
            {
                //你这里注意先判断一下就好了
                if (m->next==NULL)
                     break;
                m = m->next;
                n = n->next; 
                if(t->data<=m->data)
                {
                    n->next = t;
                    t->next = m;
                    break; 
                }
            }
        /*  if(m->next==NULL)
                 m->next=t;*/
            if(m->data<t->data) 
               m->next = t; 
        }
        scanf("%d",&x);
   }
}
void output(list *head)
{
    list *p;
    p=head->next;
    while (p)
    {
        printf("%d ",p->data);
        p=p->next;
    }
}
int main(void)
{
     //创建一个有头结点的链表 
     printf("create a list");
     list *head = NULL;
     head = create(head);
     insert(head);
     output(head);
     return 0; 
} 

楼主，添加个输出函数，把链表输出，看看对不对

代码中有个scanf("%d",x);少了&，应该为scanf("%d",&x);

帮你修改了一下：

 #include <stdio.h>
#include <malloc.h>
#define ElemType int
#define OVERFLOW 0
#define OK 1
typedef struct node
{ 
ElemType data; 
struct node *next;
}list;
list* create(list *head)
{
    list *t; 
    t=(list*)malloc(sizeof(list));
    if(!t)
    { 
    printf("\n分配空间失败！"); 
    return (OVERFLOW); 
    }
    head = t; 
    int x; 
    printf("\nenter a number(end with $):"); 
    scanf("%d",&x);
     if(x!='$')
     {
        t=(list*)malloc(sizeof(list)); 
        t->data = x;
        t->next = NULL;
         head->next = t;
     }
     return head;
}
void insert(list *head)
{
    list *t,*m,*n;
//m和n表示相邻的两个节点，用于与节点比较大小，然后插入 
    int x;
    scanf("%d",&x); 
    while(x!=0)
    {
        t=(list*)malloc(sizeof(list)); 
        if(!t)
        return;
        t->data = x; 
        t->next = NULL; 
        m = head->next;
        //这里调试出现错误 
        n = head;
        if(t->data <= m->data)
        {
            n->next = t;
            t->next = m;
        }
        else
        {
            while(1)
            {
                m = m->next;
                n = n->next; 
                if(t->data<=m->data)
                {
                    n->next = t;
                    t->next = m;
                    break; 
                }
                if (m->next==NULL)
                     break;
            }
        /*  if(m->next==NULL)
                 m->next=t;*/
            if(m->data<t->data) 
               m->next = t; 
        }
        scanf("%d",&x);
   }
}
void output(list *head)
{
    list *p;
    p=head->next;
    while (p)
    {
        printf("%d ",p->data);
        p=p->next;
    }
}
int main(void)
{
     //创建一个有头结点的链表 
     printf("create a list");
     list *head = NULL;
     head = create(head);
     insert(head);
     output(head);
     return 0; 
} 

  if(x!=0){
        t=(list*)malloc(sizeof(list));
        t->data = x;
        t->next = NULL;
        if(x > head->next->data){
            head->next->next = t;
        } else{
            t->next = head->next;
            head->next = t;
        }
    }
    scanf("%d",&x);

因为第一次进入这个函数的时候只有一个首元节点，所以m=m->next；之后的m->data是非法的

我输入的是1 2 3 4 5 0