c++ - 合并两个 LinkedList 而不创建一个新的 LinkedList

Question

我正在尝试获取可执行文件中的两个链表，并在交替位置将它们合并到一起。前任。 ListOne 1,2,3 和 ListTwo 4,5 新的 ListOne 应该是 1,4,2,5,3。

链表.h文件:

class LinkedList
{
private:
struct ListNode
{
    string firstName;
    string lastName;
    long int phoneNumber;
    struct ListNode *next;
};
ListNode *head;

public:
LinkedList()
{
    head = nullptr;
}
~LinkedList();
void appendNode(string f, string l, long int p);
void displayList();
};

链表 .cpp 文件:

LinkedList::~LinkedList()
{
cout << "LinkList destructor" << endl;
}

void LinkedList::appendNode(string f, string l, long int p)
{
    ListNode *newNode;
    ListNode *nodePtr;
    newNode = new ListNode;

    newNode -> firstName = f;
    newNode -> lastName = l;
    newNode -> phoneNumber = p;
    newNode -> next = nullptr;

    if (!head)
        head = newNode;

    else
    {
        nodePtr = head;

        while (nodePtr -> next)
            //while nodePtr is pointing to another node
            nodePtr = nodePtr -> next;
            //move to that node

        nodePtr -> next = newNode;
        //inset the newNode at the end of the linked list
    }
 }

 void LinkedList::displayList()
{
    ListNode *nodePtr;
    nodePtr = head;

    while(nodePtr)
    //while nodePtr is true, meaning there is a node in the list
    {
        cout << nodePtr -> firstName << endl;
        cout << nodePtr -> lastName << endl;
        cout << nodePtr -> phoneNumber << endl;
        nodePtr = nodePtr -> next;
     }
}

可执行文件:

LinkedList ListOne;
LinkedList ListTwo;

ListOne.appendNode("Cate", "Beckem", 7704563454);
ListOne.appendNode("Cabe","Tomas", 7703451523);

ListTwo.appendNode("Mary", "Smith", 4043456543);
ListTwo.appendNode("Mark", "Carter", 4045433454);

我的程序运行完美，包括 displayList 函数。我只是很困惑如何着手制作合并功能。

Answer 1

做一个合并函数并不难。可以只用一个新的head来记录新的list，然后遍历这两个list，依次将这两个list中的结点移动到new list中，如下所示。

 LinkedList LinkedList::merge(LinkedList b)
{
    // if one list is null, return the other
    if (this->head == nullptr)
        return b;
    if (b.head == nullptr)
        return *this;

    LinkedList newlist;
    ListNode *ap = this->head, *bp = b.head, *p = nullptr;
    // if two pointer is all not null, move node from these to new list in turn
    while (ap != nullptr && bp != nullptr)
    {
        if (newlist.head == nullptr)
        {
            p = newlist.head = ap;
            ap = ap->next;
            p = p->next = bp;
            bp = bp->next;
        }
        else
        {
            p = p->next = ap;
            ap = ap->next;
            p = p->next = bp;
            bp = bp->next;
        }
    }
    // maybe one list is longer, and there is some node left.
    if (ap != nullptr)
        p->next = ap;
    if (bp != nullptr)
        p->next = bp;
    //clear original list
    this->head = b.head = nullptr;
    //if you want to merge list b to the caller list, you can change to
    //this->head = newlist->head and beginning part also need some modification.
    return newlist;
}

也许您不想更改原始列表，那么您可以只复制值并为新列表创建新节点。