将项目附加到链接列表

Question

所以我完全不知道如何将节点附加到我的链表中。基本上，我有一个 Inventory 对象（链表），由包含 ItemStack 对象的节点组成。这个 ItemStack 对象包含一个项目的名称和该项目的数量。在我的 Inventory.cpp 文件中，我有一个名为 addItems() 的函数，它有一个 ItemStack 参数。

由于某种原因，当我尝试将 ItemStack 节点附加到列表末尾并输出结果时，唯一的输出是第一个和最后一个 ItemStack。它跳过了中间的 ItemStack 节点。我不确定它们是否只是被覆盖或发生了什么。我知道这与我的 Inventory.cpp 文件或 Inventory.h 文件有关，因为我不允许修改任何其他文件。

这个程序的输入是从两个文件中读取的。 itemList-01.txt 和 inventoryList-01.txt。此外，库存中占用的插槽数量不会被更新。如果有人愿意对我遇到的问题有所了解，我将不胜感激。我已经做了好几天了，没有任何进展。如果以下代码不够有用，我将附上我所有代码的链接。（请记住，只有库存.CPP 和库存.H 可以修改）。提前致谢。

https://github.com/brussell757/CS330/tree/master/Assignment_1

库存开始.H 文件

   #ifndef INVENTORY_H_INCLUDED
   #define INVENTORY_H_INCLUDED

   #include <iostream>

   #include "ItemStack.h"

   /**
   * An Inventory is composed of n slots. Each slot may store only
   * one type of item--specified by *slots*. 
   * <p>
   * Once all slots are filled, no additional Item types may be
   * stored. Individual slots may contain any number of the same 
   * Item.
   */
    class Inventory{
    private:
    /**
     * Each Node represents one Inventory slot--i.e., space
     */
    struct Node{
        ItemStack data; ///< One ItemStack
        Node *next;     ///< Next ItemStack Node

        /**
         * Create an empty *Air* Node
         */
        Node();

        /**
         * Create a Node that contains an ItemStack, *s*
         */
        Node( ItemStack s );
    };

    Node *first;  ///< First inventory slot
    Node *last;   ///< Last inventory slot

    int slots;    ///< Capacity
    int occupied; ///< Number of occupied slots

    /**
     * Disassembles the list for Deconstructor
     */
    void disassemble();

    public:
    /**
     * Default to 10 slots
     */
    Inventory();

    /**
     * Create an inventory with n slots
     *
     * @pre n > 0
     */
    Inventory( int n );

    /**
     * Copy an already existing Inventory
     */
    Inventory( const Inventory &src );

    /**
     * Destruct an Inventory
     */
    ~Inventory();

    /**
     * Add one or more items to the inventory list
     *
     * @return true if *stack* was added and false otherwise
     */
    bool addItems( ItemStack stack );

    /**
     * Print a Summary of the Inventory and all Items contained within
     */
    void display( std::ostream &outs ) const;

    /**
     *
     */
    Inventory::Node* begin() const;

    /**
     *
     */
    Inventory::Node* end() const;

    /**
     * Overloaded assignment operator for Inventory
     */
    Inventory& operator=( const Inventory &rhs );
    };

   /**
   * Print the Inventory through use of the display member function
   */
inline std::ostream& operator<<(std::ostream &outs, const Inventory &prt)    {
   prt.display( outs );
   return outs;
}

   #endif

库存开始.CPP 文件

    /**
    * Used to add items to the Inventory
    */
    bool Inventory::addItems ( ItemStack stack ){

    Node* new_node = nullptr;

    // Sets new_node equal to a new node containing the current ItemStack
    new_node = new Node(stack);

    // Insert ItemStack into empty Inventory
    if(this->first == nullptr) {

        // Sets the first node in the Inventory to the new Node
        this->first = new_node;

        // Sets the last node in the Inventory to the new Node
        this->last = new_node;

        // Increase the number of occupied slots by 1
        occupied++;

        return true;

    } else {

        // Statement that executes if the maximum number of slots in the Inventory have not been filled
        if(occupied <= slots) {

            // Sets current node to the head
            Node *curr = this->first; 

            // Sets trail node to nullptr
            Node *trail = nullptr;

            // Traverse the list
            while(curr != nullptr) { 

                // Sets the (first->next) node to the new_node (new ItemStack)
                curr->next = new_node; 

                // Sets the trail node to the current node (first)
                trail = curr;

                // Sets the current node to the node after new_node (nullptr)
                curr = new_node->next;

                return true;

            }

            // Increase the number of occupied slots by 1
            occupied++;

        } else {

            return false;

        }

    }

} 

Answer 1

在您的循环中，您应该遍历列表直到到达末尾。一旦你到达列表的末尾，然后你添加节点。

未经过测试，但您很可能应该这样做：

    Node *curr = this->first; 
    Node *temp = curr; 
    while(curr != nullptr) 
    { 
        temp = curr;
        curr = curr->next;
    }
    temp->next = new_node;
    new_node->next = nullptr;
    last = new_node;

这只是遍历列表直到它到达末尾。临时跟踪最后一个节点。然后，一旦完成，您只需将最后一个有效节点指向新节点。