在C ++中将节点从一个队列移动到另一个队列[重复]

Question

我在程序中将节点从一个队列移动到另一个队列时遇到问题。我在 C++ 中使用单链表实现队列。我正在制作电晕测试程序。队列有testingQueue、quarantineQueue和homeQueue三个对象。用户将人员一一添加到测试队列中，添加后，用户从测试队列中逐一检查每个人是否进行电晕测试（使用FIFO方法，因为它是一个队列）。测试结果是随机的，可以是阳性或阴性。如果结果为正，则将该人发送到隔离队列，如果结果为负，则将该人发送到 homeQueue。我的程序运行良好，没有错误，但是当一个人被发送到隔离队列之后，我为隔离队列运行 displayQueue() 函数，它没有显示任何人在那里。请帮忙。

完整代码：

#include <string>
#include <stdlib.h>
#include <cstdlib>
using namespace std;

class Person {
public:
    string name;
    string gender;
    int age;
    string testType;
    string result;
    Person* next;
    Person() {
        testType = "Corona Test";
    }
};

class Queue {
public:
    Person* rear;
    Person* front;
public:
    Queue() {
        rear = NULL;
        front = NULL;
    }
    void addPerson() {
        Person* temp = new Person;
        cout << "Enter Name Of The Person: ";
        cin.ignore();
        getline(cin, temp->name);
        cout << "Enter Gender Of The Person: ";
        cin >> temp->gender;
        cout << "Enter Age Of The Person: ";
        cin >> temp->age;
        temp->next = NULL;
        if (front == NULL) {
            front = temp;
            rear = temp;
        }
        else {
            rear->next = temp;
            rear = temp;
        }
    }

    void checkPerson(Queue qq,Queue hq) {
        Person* temp = front;
        int a = rand() % 100 + 1;
        if (a < 50) {
            temp->result = "Positive";
            if (qq.front == NULL) {
                front = temp->next;
                qq.front = temp;
                qq.rear = temp;
                temp->next = NULL;
            }
            else {
                front = temp->next;
                qq.rear->next = temp;
                qq.rear = temp;
                temp->next = NULL;
            }
            cout << "Result Was Positive And Person Has Been Moved To Quarantine." << endl;
        }
        else {
            temp->result = "Negative";
            if (hq.front == NULL) {
                front = temp->next;
                hq.front = temp;
                hq.rear = temp;
                temp->next = NULL;
            }
            else {
                front = temp->next;
                hq.rear->next = temp;
                hq.rear = temp;
                temp->next = NULL;
            }
            cout << "Result Was Negative And Person Has Been Moved To Home." << endl;
        }
    }

    void displayQueue() {
        Person* temp = front;
        while (temp != NULL) {
            cout << endl;
            cout << "Name Of Person: " << temp->name << endl;
            cout << "Gender Of Person: " << temp->gender << endl;
            cout << "Age Of Person: " << temp->age << endl;
            cout << "Test Type Of Person: " << temp->testType << endl;
            cout << "Result Of Person: " << temp->result << endl << endl;
            temp = temp->next;
        }
    }
};

void menu() {
    cout << "\n\n\t\t\t\t   ----------------------------------------------------\n";
    cout << "\t\t\t\t   |        1.Add a Person To Testing Queue           |\n";
    cout << "\t\t\t\t   |       2.Check a Person From Testing Queue        |\n";
    cout << "\t\t\t\t   |     3.Recover a Person From Quarantine Queue     |\n";
    cout << "\t\t\t\t   |      4.Display All People In Testing Queue       |\n";
    cout << "\t\t\t\t   |     5.Display All People In Quarantine Queue     |\n";
    cout << "\t\t\t\t   |         6. Display All People At Home            |\n";
    cout << "\t\t\t\t   |               7. Exit Program                    |\n";
    cout << "\t\t\t\t   ----------------------------------------------------\n";
}

int main() {
    Queue testingQueue, quarantineQueue, homeQueue;
    int op;
Fahad:
    menu();
    cout << "Enter Option: ";
    cin >> op;
    switch (op) {
    case 1:
        testingQueue.addPerson();
        cout << "A Person Has Been Added To Testing Queue." << endl;
        system("pause");
        system("cls");
        goto Fahad;
    case 2:
        testingQueue.checkPerson(quarantineQueue, homeQueue);
        system("pause");
        system("cls");
        goto Fahad;
    case 3:
        system("pause");
        system("cls");
        goto Fahad;
    case 4:
        testingQueue.displayQueue();
        system("pause");
        system("cls");
        goto Fahad;
    case 5:
        quarantineQueue.displayQueue();
        system("pause");
        system("cls");
        goto Fahad;
    case 6:
        homeQueue.displayQueue();
        system("pause");
        system("cls");
        goto Fahad;
    case 7:
        return 0;
    default:
        cout << "Invalid Option." << endl;
        system("pause");
        system("cls");
        goto Fahad;
    }
    system("pause");
}

Answer 1

考虑复制 std::queue 的接口：

back    Returns a reference to the last element of the queue.
front   Returns a reference to the first element of the queue.
pop     Removes an element from the front of the queue.
push    Adds an element to the back of the queue.
empty   Tests if the queue is empty.
size    Returns the number of elements in the queue.
~Person deletes all nodes in the queue, then deletes the queue.

您可以考虑更改接口以使用指向节点的指针，并添加另外两个函数，而不是不断地分配和释放节点：

new     creates a node, returns a pointer to the node.
delete  deletes a node (input parameter is pointer to node).
back    Returns a pointer to the last  node of the queue.
front   Returns a pointer to the first node of the queue.
pop     Returns a pointer to what was the first node of the queue, which is now removed.
push    Appends an element via pointer to the back of the queue.
empty   Tests if the queue is empty.
size    Returns the number of elements in the queue.
~Person deletes all nodes in the queue, then deletes the queue.