c++ - c++删除一系列节点

Question

大家好，我是这里的新手，也是编程方面的新手。我正在尝试删除链表中的一系列节点，但不知道如何操作。我尝试使用 for 循环，但是由于我向我的删除函数传递了一个字符串，所以我无法递增节点以使其删除到最终计数。任何帮助将不胜感激!

 #include <iostream>
    #define nullptr 0
    #include <cstdlib>
    #include <algorithm>
    #include <string>
    #include <conio.h>



    using namespace std;
    int menu();

    class ItemList {
        private:
            struct ListNode{
                string IName;
                string QQuantity;
                string PPrice;
                double value;
                struct ListNode * next;
                    };
    ListNode *head;
        public:
            ItemList()
                {
                    head = new ListNode;
                    head->next=nullptr;
                }
                ~ItemList();

                void insertNode(string Item, string Quantity, string Price)
                {
                    ListNode *newNode;
                    ListNode *nodePtr;
                    ListNode *previousNode=nullptr;

                    newNode=new ListNode;
                    newNode->IName=Item;
                    newNode->QQuantity=Quantity;
                    newNode->PPrice=Price;

                    if(!head)
                    {
                        head=newNode;
                        newNode->next=nullptr;
                    }
                    else
                    {
                        nodePtr=head;
                        previousNode=nullptr;

                        while(nodePtr != nullptr && nodePtr->IName < Item)
                        {
                            previousNode=nodePtr;
                            nodePtr=nodePtr->next;
                        }
                        if(previousNode==nullptr)
                        {
                            head=newNode;
                            newNode->next=nodePtr;
                        }
                        else
                        {
                            previousNode->next=newNode;
                            newNode->next=nodePtr;
                        }
                    }
                }
                void displayNode()
                {
                    ListNode *nodePtr;
                    nodePtr=head->next;

                    while(nodePtr)
                    {
                        cout << nodePtr->IName << ",  ";
                        cout << nodePtr->QQuantity << "  ";
                        cout << "$" << nodePtr->PPrice << "\n" << endl;
                        nodePtr=nodePtr->next;
                    }
                }
                void modifyNode(string Item)
                {
                ListNode *nodePtr;
                ListNode *nodePrev;
                string newName, newQuantity, newPrice;
                int modify;
                if (!head)
                {
                    return;
                    cout << "Store is empty." << endl;
                }
                else
                {
                    nodePtr = head;
                    if (head->IName==Item)
                        nodePtr = head->next;
                    else
                    {
                        while (nodePtr != nullptr && nodePtr->IName != Item)
                        {
                            nodePrev = nodePtr;
                            nodePtr = nodePtr->next;
                        }
                    }
                    if (nodePtr)
                    {
                        cout << nodePtr->IName << "\t" << nodePtr->QQuantity << "\t" << nodePtr->PPrice << endl;
                        cout << "What would you like to change?\n";
                        cout << "1. Item" << endl;
                        cout << "2. Quantity" << endl;
                        cout << "3. Price" << endl;
                        cout << "4. Whole Entry" << endl;
                        cin >> modify;

                        transform(newName.begin(), newName.end(), newName.begin(), ::toupper);
                        switch (modify)
                        {
                            case 1:
                                cout << "Change to what?\n";
                                cin >> newName;
                                nodePtr->IName = newName;
                                break;
                            case 2:
                                cout << "Change to what?\n";
                                cin >> newQuantity;
                                nodePtr->QQuantity = newQuantity;
                                break;
                            case 3:
                                cout << "Change to what?\n";
                                cin >> newPrice;
                                nodePtr->PPrice = newPrice;
                                break;
                            case 4:
                                cout << "Change to what?\n";
                                cin >> newName;
                                nodePtr->IName = newName;
                                cout << "Change to what?\n";
                                cin >> newQuantity;
                                nodePtr->QQuantity = newQuantity;
                                cout << "Change to what?\n";
                                cin >> newPrice;
                                nodePtr->PPrice = newPrice;
                        }
                    }
                    else
                        cout << "Person not found\n";
                }
            }

                void deleteNode(string Item)
                {
                    ListNode *nodePtr;
                    ListNode *previousNode;

                    if(!head)
                        return;
                    if(head->IName==Item)
                    {
                        nodePtr=head->next;
                        delete head;
                        head=nodePtr;
                    }
                    else
                    {
                        nodePtr=head;
                        while(nodePtr!=nullptr && nodePtr->IName!=Item)
                        {
                            previousNode=nodePtr;
                            nodePtr=nodePtr->next;
                        }
                        if(nodePtr)
                        {
                            previousNode->next=nodePtr->next;
                            delete nodePtr;
                        }
                        else
                        {
                            cout << "Nothing to delete." << endl;
                        }
                    }
                }
            };


    ItemList::~ItemList()
    {
        ListNode *nodePtr;
        ListNode *nextNode;

        nodePtr=head;
        while(nodePtr!=nullptr)
        {
            nextNode=nodePtr->next;
            delete nodePtr;
            nodePtr=nextNode;
        }
    }

    int main()
    {
        ItemList pro;
        int method;
        while(method!=0)
        {
        int method=menu();
        system("cls");
        string It, Q, P;
        switch(method)
        {
        case 1:
            int count;
            cout << "How many products would you like to put in?" << endl;
            cin >> count;
            system("cls");
            for(int i=0; i<count; i++)
            {
                cout << "Product #" << i + 1 << endl;
                cout << "Enter the item name: ";
                cin.sync();
                getline(cin,It);
                transform(It.begin(), It.end(), It.begin(), ::toupper);
                cout << "Enter the Quantity: ";
                cin >> Q;
                transform(Q.begin(), Q.end(), Q.begin(), ::toupper);
                cout << "Enter the Price: ";
                cin >> P;
                pro.insertNode(It, Q, P);
                cout << "\n";
            }
            break;

        case 2:
            pro.displayNode();
            break;

        case 3:
            pro.displayNode();
            cout << "What product do you wish to modify? (by item name)" << endl;
            cin.sync();
            getline(cin, It);
            transform(It.begin(), It.end(), It.begin(), ::toupper);
            system("cls");
            pro.modifyNode(It);
            break;

        case 4:
            int del;
            cout << "Do you wish to delete one product or more?" << endl;
            cout << "1. One" << endl;
            cout << "2. Range of Products" << endl;
                cin >> del;
                system("cls");
                switch(del)
                {
                    case 1:
                        cout << "What product do you wish to delete? (by item name)" << endl;
                        pro.displayNode();
                        cout << "\n";
                        cin.sync();
                        getline(cin,It);
                        transform(It.begin(), It.end(), It.begin(), ::toupper);
                        pro.deleteNode(It);
                        cout << "\n";
                        break;
                    case 2:
                        int count;
                        cout << "How many?";
                        cin >> count;
                        pro.displayNode();
                        cout << "Starting where?" << endl;
                        cin >> It;
                        transform(It.begin(), It.end(), It.begin(), ::toupper);
                        for(int i=0; i<count; i++)
                        {
                            pro.deleteNode(It);
                            It(i);
                        }
                        break;
                }
            break;

        case 5:
            pro.~ItemList();
            cout << "All items deleted." << endl;
            break;

        case 0:
            cout << "Exiting the program." << endl;
            return 0;
        }
        system("pause");
        system("cls");
        }
        return 0;
    }

    int menu()
    {
        string space1= "                    ";
        string space2= "                                  ";
        int method;
        cout << space1 << "What would you like to do to the Phone Book?" << endl;
        cout << space2 << "1. Insert" << endl;
        cout << space2 << "2. Display" << endl;
        cout << space2 << "3. Modify" << endl;
        cout << space2 << "4. Delete" << endl;
        cout << space2 << "5. Empty" << endl;
        cout << space2 << "0. Exit\n" << endl;
        cout << space2;
        cin >> method;
        return(method);
    }

Answer 1

您可以创建一个函数来检索给定名称的节点指针，然后将“deleteNode”函数更改为通过指针而不是名称删除的函数，而不是通过节点名称 (IName) 进行删除。此外，此函数应返回可用于删除后续节点的下一个节点指针(如果列表中没有其他元素，则返回 null)。

编辑:非常基本的代码示例:

char * get_pointer_by_name(string Name)
{
    ListNode * curr_node = this->head;

    while(curr_node != NULL)
    {
        if(curr_node->IName == Name)
        {
            return (char *) curr_node;
        }
        else
        {
            curr_node = curr_node->next;
        }
    }

    // node not found

}

char * delete_node(char * pointer)
{
    char * tmp = (char *) (ListNode *) pointer->next; // check this, it may be wrong
    // this is a very simple and illustrative way to delete your node, not the right one
    delete pointer;
    // return the next node pointer
    return tmp;
}

完成后，您所要做的就是使用 get_pointer_by_name() 获取要删除的节点，然后迭代几次以删除剩余的节点，就像这样:

char * tmp = get_pointer_by_name("name");

while(tmp != NULL && count > 0)
{
    tmp = deleteNode(tmp);
    count--;
}