C语言 为什么这个链表顺序插入段错误

Question

我正在编写一个程序，该程序按排序顺序插入链表，但它不断出现分段错误，我不知道为什么。我怀疑它与指针有关，但我不能说，因为在我的编程生涯中，这些对我来说仍然有点困惑。此外，我必须保持插入原型相同。我不能将node参数更改为双指针。谢谢!

#include <stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include<conio.h>
typedef struct node {
    int data;
    struct node  *next;
};
int main ()
{
    struct node* first;  
    int temp,x,y;
    struct node *create (struct node *first);
    first = NULL;     
    void display (struct node *first);
    printf ("nnCreating a Linked Listn");
    printf ("nEnter Element: ");
    scanf ("%d", &x);
    y=x;
    while(y>0)
    {
        scanf ("%d", &x);
        insert_sorted_linked_list(first,x); 
        y--;
    }
    printf ("nThe list after creation is: ");
    display (first);
    printf ("nThe sorted list is: ");
    display (first);
    return(0);
}   /*END OF MAIN*/
insert_sorted_linked_list(struct node* head, int val)
{
    struct node* pCur;
    struct node* pNew = (struct node*) (malloc(sizeof(struct node)));
    pNew -> data = val;
    pNew ->next = NULL;
    pCur = head;
    if( pCur->data == NULL )
    {
        head->data = pNew->data;
        head->next = NULL;
    }
    else if (pNew->data  <   pCur->data)
    {
        pNew ->next = pCur ;
        head = pNew;
    }
}
void display (struct node *first)
{   struct node *save;         /*OR sort *save     */
    if (first == NULL)
        printf ("nList is empty");
    else
    {  save = first;
        while (save != NULL)
        {   printf ("-> %d ", save->data);
            save = save->next;
        }
        getch();
    }
    return;
}   

EDIT:将main改为int。调试器不喜欢这样的行:

struct node* pNew = (struct node*) (malloc(sizeof(struct node)));

if(pCur->data == NULL)

不知道出了什么问题。

编辑2:

我决定我不打算让它原来的工作方式，他要求它在明天早上之前，所以我去了一个修改版本张贴在这里。那一个没有发现错误，但原来还有一个逻辑错误。

#include <stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include<conio.h>
typedef struct s
{
    int data;
    struct s  *next;
}node;

void insert_sorted_linked_list(node **head, int val);
void display (node **first);
void freeList(node **first);
int main ()
{
    node* first;
    int x,y;
    first = NULL;
    printf ("nnCreating a Linked Listn");
    printf ("nEnter number of elements: ");
    scanf ("%d", &x);
    y=x;
    while(y>0)
    {
        scanf ("%d", &x);
        insert_sorted_linked_list(&first,x);
        y--;
    }
    printf ("nThe sorted list is: ");
    display (&first);
    freeList(&first);
    return 0;
}
void insert_sorted_linked_list(node **head, int val)
{
    node* pCur;
    node* pNew = (node*) (malloc(sizeof(node)));
    pNew->data = val;
    pNew->next = NULL;
    pCur = (*head);
    if( pCur == NULL )
    {
        (*head) = pNew;
    }
    else if(pNew->data  <   pCur->data)
    {
        pNew->next = pCur;
        (*head) = pNew;
    }
    else
    {
    while(pCur->next!=NULL && pNew->data  >  pCur->next->data)
        pCur = pCur->next;
    pNew->next = pCur->next;
    pCur->next = pNew;
    }
}

void display (node **first)
{
    node *lisprint;         /*OR sort *lisprint     */
    if (*first == NULL)
    printf ("nList is empty");
    else
    {
        lisprint = *first;
        while (lisprint != NULL)
        {
            printf ("-> %d ", lisprint->data);
            lisprint = lisprint->next;
        }
        getch();
    }
}   /*END OF FUNCTION DISPLAY*/
void freeList(node **first)
{
    node *i;
    i = *first;
    while(i !=NULL)
    {
        (*first) = (*first)->next;
        free(i);
        i = *first;
    }
}

谢谢!

Answer 1

请正确格式化您的代码!光是看看错误在哪里就很痛苦了!事实上，

/*PROGRAM TO CREATE & THEN DISPLAY THE LINKED LIST IN SORTED FORM*/
#include <stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include<conio.h>
typedef struct s
{
    int data;
    struct s  *next;
}node; 
/* your declaration for typedef was incorrect. We use typedef in C for structures so   that we do not have to repeat struct s everytime. Using typedef, we can write node as we do in c++ */
void insert_sorted_linked_list(node **head, int val); /* do not need to return anything, as well as see the parameter. When we want to change a pointer, we pass the address to the pointer, as it results in passing by value */
void display (node **first); /* same here and below */
void freeList(node **first); /* if you don't do this, memory leak!!! */
int main ()
{
    node* first;  /*OR sort *first,*list,*pass  */
    int temp,x,y;
    first = NULL;      /*OR sort *create()  */
    printf ("nnCreating a Linked Listn");
    printf ("nEnter number of elements: "); /* specify what you want the user to enter */
    scanf ("%d", &x);
    y=x;
    while(y>0)
    {
        scanf ("%d", &x);
        insert_sorted_linked_list(&first,x); /*CALLING CREATE FUNCTION, notice the &first*/
        y--;
    }
    printf ("nThe list after creation is: ");
    display (&first);
    printf ("nThe sorted list is: ");
    display (&first);
    freeList(&first);
    return 0;
}   /*END OF MAIN*/
void insert_sorted_linked_list(node **head, int val)
{
    node* pCur;
    node* pNew = (node*) (malloc(sizeof(node)));
    pNew->data = val;
    pNew->next = NULL;
    pCur = (*head);
    if( pCur == NULL )
    {
        (*head) = pNew;
    }
    else if (pNew->data  <   pCur->data)
    {
        pNew->next = pCur ;
        (*head) = pNew;
    }
}
/*DISPLAY FUNCTION*/
void display (node **first)
{
    node *save;         /*OR sort *save     */
    if (*first == NULL)
    printf ("nList is empty");
    else
    {
        save = *first;
        while (save != NULL)
        {
            printf ("-> %d ", save->data);
            save = save->next;
        }
        getch();
    }
}   /*END OF FUNCTION DISPLAY*/
void freeList(node **first)
{
    node *i;
    i = *first;
    while(i !=NULL)
    {
        (*first) = (*first)->next;
        free(i);
        i = *first;
    }
}