如何在链表的末尾添加元素 [英] How to add elements to the end of a linked list

问题描述

所以我试图在C ++中创建一个函数，应该在链表的末尾添加一个元素。
添加元素的函数应该在 main -method中调用。
即使列表中没有元素，也应该可以调用它。

So I am trying to create a function in C++ that should add an element at the end of an linked list. This function that adds the elements should be called within the main-method. It should be possible to call it even if there is no element in the list.

我到目前为止是以下内容：

What I have so far is the following:

int main()
{
   ListElement* l = new ListElement;
   l->digit = 9;
   l->next = NULL;
   appendList(l, 5);
   appendList(l, 7);

   printList(l);

   return 0;
}

void appendList(ListElement *&l, int newDigit)
{
    ListElement *lh = new ListElement;

    if(l == NULL)
    {
        l->digit = newDigit;
        l->next = NULL;
    }
    else
    {
        lh=l;

        while(lh != NULL)
        {
           lh=lh->next;
        }
        lh=lh->next;
        lh->digit = newDigit;
        lh->next = NULL;
        l = lh;
    }
}

不幸的是，它不工作。我试图删除或添加参数 - 没有帮助，我找不到一个合适的答案在互联网上。
所以，如果你能帮助我，我会很高兴，因为我在这里绝望。

Unfortunately it just isn't working. I've tried removing or adding parameters - nothing helped and I couldn't find an appropriate answer on the internet. So if anyone of you could help me, I'd be very, very happy because I'm kind of despairing here...

推荐答案

尝试以下操作：

void appendList( ListElement * &head, int newDigit )
{
    if ( head == 0 )
    {
        head = new ListElement;

        head->digit = newDigit;
        head->next  = 0;
    }
    else
    {
        ListElement *next = head;

        while ( next->next ) next = next->next;

        next->next = new ListElement;
        next->next->digit = newDigit;
        next->next->next  = 0;
    }
} 


int main()
{
    ListElement *head = 0;

    appendList( head, 9 );
    appendList( head, 5 );
    appendList( head, 7 );

    printList( head );

    return 0;
}

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