C链表和节点程序，为什么会出现未处理的异常？

Question

如何修复我在运行程序中不断遇到的错误？我试图让 head 指向 first 的地址，然后能够通过一个将创建新节点的函数传递 *first，用户可以在运行时间给它数据，然后 first 将指向到新节点！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;
    }
}

这有效。

你应该考虑的几点：

1) 是int main，不是void main()

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

3) 当你创建一个新节点时，你没有将它的 next 设置为 NULL。这个不见了。 newNode->next = NULL;

4) 你陷入了无限循环。 option 从未更新过。我补充说。此外，菜单应在用户做出选择后显示。

5) 没有检查内存分配。如果malloc returns NULL怎么办？

6) 您对 first 和 head 感到困惑。约定是使用head。

7) 我每次都会使用 typedef 而不是 struct node 。这留作练习:)

OP，此列表并不详尽。

如果你想倒序显示数字，把addToStart中的else部分改成这样

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);

    }
}

C链表和节点程序，为什么会出现未处理的异常？

C linked list and nodes program, why am I getting a unhanded exception?

c

malloc

linked-list

unhandled-exception

nodes