c - 带有不需要的零的链表

Question

我环顾四周，不确定它是否已发布，但我正在尝试在 C 中创建两个链表。当它们应该为“空”时，它们为零。我不确定这些零是从哪里来的，这让我很困惑。

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

struct node
{
    int price;
    int bookNumber;

    struct node * next;

};


void addNode(struct node* pHead, int pPrice, int pBookNumber);
void displayList(struct node* pHead);
void removeNode(struct node* pHead, int pBookNumber);

int main()
{

    struct node* head1;
    head1 = (struct node*)malloc(sizeof(struct node));
    head1 -> next = NULL;

    addNode(head1, 10, 1234);
    addNode(head1, 35, 9876);
    displayList(head1);
    printf("\n");
    struct node* head2;
    head2 = (struct node*)malloc(sizeof(struct node));
    head2 -> next = NULL;
   // addNode(head2,13, 8888);
    displayList(head2);

}

void addNode(struct node* pHead, int pPrice, int pBookNumber)
{

    struct node* newNode;
    struct node* ptr;

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

    newNode -> price = pPrice;
    newNode -> bookNumber = pBookNumber;

    newNode -> next = NULL;

    ptr = pHead;

    if(pHead -> next == NULL)
    {
        pHead -> next = newNode;
        newNode -> next = NULL;
    }
    else
    {
        while((ptr -> next != NULL))
        {
            ptr = ptr -> next;
        }

        ptr -> next = newNode;
        newNode -> next = NULL;

    }

}

void removeNode(struct node* pHead,int pBookNumber)
{

    struct node *current, *prev;
    current = pHead;
    /*searching list for the desired data*/
    while((current -> bookNumber != pBookNumber))
    {

        prev = current;

        current = current -> next;

    }

    /*fixing links between nodes*/
    prev -> next = current -> next;

    /*freeing memory*/
    free(current);

    /*removing from end of list*/
    if((current -> next = NULL))
    {

        prev -> next = NULL;

        /*freeing memory*/
        free(current);

    }

}

void displayList(struct node* pHead)
{
        while(pHead != NULL)
        {
            printf("$%d, book# %d -> ", pHead -> price, pHead -> bookNumber);
            pHead = pHead -> next;
        }
        printf("NULL");

    }

我在第一个列表中添加了两个条目，但没有在第二个列表中添加任何内容...这是输出:

$0, book# 0 -> $10, book# 1234 -> $35, book# 9876 -> NULL
$0, book# 0 -> NULL
Process returned 0 (0x0)   execution time : 0.001 s
Press ENTER to continue.

Answer 1

第一个值得注意的问题是您似乎有一个虚拟节点
在列表的开头

struct node* head1;
head1 = (struct node*)malloc(sizeof(struct node));
head1 -> next = NULL;

但是你从 head 开始打印而不是从 head->next
即包括虚拟节点。