C 链表和节点程序，为什么我得到一个不手动的异常

Question

如何

修复运行程序时不断出现的错误？我试图让头指向第一个地址，然后能够首先通过将创建新节点的函数传递*，用户可以在运行时为其提供数据，然后首先指向新节点！我这样做对吗？

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
void addToStart (struct node** head);
void Menu();
void DisplayList(struct node* head);
struct node{
    int data;
    struct node *next;
};

void main(){
    int option = 0;
    struct node *head;
    struct node *first;
    head = (struct node*)malloc(sizeof(struct node));
    first = (struct node*)malloc(sizeof(struct node));
    head->data= 0;
    head->next = first;
    first->data = 1;
    first->next = NULL;
    Menu();
    scanf(" %d", option);
    while(option != 6){
        switch(option){
        case 1:
            addToStart(&first);
            break;
        case 3:
            DisplayList(head);
        break;
    case 6:
        exit(0);
        break;
    default:
        printf("nTry Again");
        break;
        }//switch end
    }//while end
}
void addToStart (struct node** first)
{
struct node *newNode;
newNode = (struct node*)malloc(sizeof(struct node));
printf("nEnter data for this node");
scanf("%d", &newNode->data);
newNode->next = *first;
*first = newNode; // transfer the address of newNode' to 'head'
}
void Menu(){
    printf("1) Add a node.n");
    printf("3) Display all nodes.n");
    printf("6) Exit.n");

}
void DisplayList(struct node* head){
    struct node *temp;
    temp =(struct node*)malloc(sizeof(struct node));
    temp = head;
    while( temp!= NULL )
    {
        printf("Data: %d", temp->data); // show the data
        temp = temp->next;
    }
}

Answer 1

#include <stdio.h>
#include <stdlib.h>

struct node{
    int data;
    struct node *next;
};
void addToStart (struct node** head);
void Menu();
void DisplayList(struct node* head);


int main(){
    int option = 0;
    struct node *head;
    //struct node *first;
    //head = (struct node*)malloc(sizeof(struct node));
    //first = (struct node*)malloc(sizeof(struct node));
    head = NULL;
    option = 0;
    while(option != 6){
        Menu();
        scanf(" %d", &option);
        switch(option){
            case 1:
                addToStart(&head);
                                break;
            case 3:
                DisplayList(head);
                                break;
            case 6:
                exit(0);
                break;
            default:
                printf("nTry Again");
                break;
        }//switch end
    }//while end
}
void addToStart (struct node** head)
{
    struct node *newNode;
    newNode = (struct node*)malloc(sizeof(struct node));
    printf("nEnter data for this node");
    scanf("%d", &newNode->data);
    newNode->next = NULL;
    if (*head==NULL)
    {
        *head = newNode;
    }
    else
    {
        struct node *lastNode = *head;
        while(lastNode->next!=NULL)
            lastNode = lastNode->next;
        lastNode->next = newNode;

    }
   // *first = newNode; // transfer the address of newNode' to 'head'
}
void Menu(){
    printf("n1) Add a node.n");
    printf("3) Display all nodes.n");
    printf("6) Exit.n");

}
void DisplayList(struct node* head){
    struct node *temp;
    temp =(struct node*)malloc(sizeof(struct node));
    temp = head;
    while( temp!= NULL )
    {
        printf("Data: %d", temp->data); // show the data
        temp = temp->next;
    }
}

这行得通。

您应该考虑的许多要点：

1）它是int main的，而不是void main()

2）当你做scanf时，给出你想要设置值的变量的地址。应该是scanf(" %d", &option);而不是scanf(" %d", option);

3） 当您创建一个新节点时，您没有将其设置为 NULL。这是不见的。 newNode->next = NULL;

4）你处于无限循环中。 option从未更新过。我补充了一句。此外，菜单应在用户给出选择后显示。

5） 不检查内存分配。如果malloc返回NULL怎么办？

6）你对first和head感到困惑。惯例是使用head。

7）我会使用typedef，而不是每次都使用struct node。这被留作一个练习:)

OP，此列表并不详尽。

如果要以相反的顺序显示数字，请像这样更改addToStart else 部分

else
    {
        newNode->next = *head;
        *head = newNode;
    }

Answer 2

#include <stdio.h>
#include <stdlib.h>

struct node{
    int data;
    struct node *next;
};
void addToStart (struct node** head);
void addToEnd (struct node** head);
void Menu();
void Size(struct node* head);
void DisplayList(struct node* head);
void SearchList(struct node* head);

int main(){
    int option = 0;
    struct node *head;
    struct node *first;
    head = (struct node*)malloc(sizeof(struct node));
    first = (struct node*)malloc(sizeof(struct node));
    head = NULL;
    option = 0;
    while(option != 6){
        Menu();
        scanf(" %d", &option);
        switch(option){
            case 1:
                addToStart(&head);
                                break;
            case 2:
                addToEnd(&head);
                break;
            case 3:
                DisplayList(head);
                                break;
            case 4:
                Size(head);
                break;
            case 5:
                SearchList(head);
                break;
            case 6:
                free(head);
                free(first);
                exit(0);
                break;
            default:
                printf("nTry Again");
                break;
        }//switch end
    }//while end
}
void addToStart (struct node** head)
{
    struct node *newNode;
    newNode = (struct node*)malloc(sizeof(struct node));
    printf("nEnter data for this node:n");
    scanf("%d", &newNode->data);
    newNode->next = NULL;
    if (*head==NULL)
    {
        *head = newNode;
    }
    else
    {
         newNode->next = *head;
        *head = newNode;
    }
    printf("%u,%u",&head,&newNode);
   // *first = newNode; // transfer the address of newNode' to 'head'
}
void addToEnd (struct node** head)
{
    struct node *newNode;
    newNode = (struct node*)malloc(sizeof(struct node));
    printf("nEnter data for this node:n");
    scanf("%d", &newNode->data);
    newNode->next = NULL;
    if (*head==NULL)
    {
        *head = newNode;
    }
    else
    {
         struct node *lastNode = *head;
         while(lastNode->next != NULL){
                lastNode = lastNode->next;
             lastNode->next = newNode;
         }
        *head = newNode;
    }
  // *first = newNode; // transfer the address of newNode' to 'head'
}
void Size(struct node* head)
    {
        int len = 0;
        struct node *temp;
        temp =(struct node*)malloc(sizeof(struct node));
        temp = head;
        while(temp != NULL)
        {
           len++;
           temp = temp->next;
        }
      printf("Size of list:  %d", len);
    }

void Menu(){
    printf("n1) Add a node.n");
    printf("2) Add node to end.n");
    printf("3) Display all nodes.n");
    printf("4) Display the length of list.n");
    printf("5) Search the list.n");
    printf("6) Exit.n");

}
void DisplayList(struct node* head){
    struct node *temp;
    temp =(struct node*)malloc(sizeof(struct node));
    temp = head;
    while( temp!= NULL )
    {
        printf("Data: %d  ", temp->data); // show the data
        temp = temp->next;
    }
}

void SearchList(struct node* head){
    int keynum;
    struct node *temp;
    temp =(struct node*)malloc(sizeof(struct node));
    temp = head;
    printf("nEnter number:n");
    scanf(" %d", &keynum);
    if(temp->data  == keynum){
        printf("n%d was found in the list!n", keynum);
    }
    else{
        printf("n%d is not in the list!n", keynum);
    }
}