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Question

C++ 新手尝试 grasp/implement 通过用户可以浏览的 maze/game 形式的第一个链表。我下面的代码可以编译，但在我输入字符串后崩溃得很厉害。

#include <iostream>
#include <string>

//main node, label is current room user is in
struct RoomNode
{
    std::string label;
    RoomNode* north;
    RoomNode* south;
    RoomNode* east;
    RoomNode* west;
    //constructor, all locations set to NULL by default
    RoomNode(std::string name)
    {
        label = name;
        north = NULL;
        south = NULL;
        east = NULL;
        west = NULL;
    }

};

int main()
{
    bool exitFound = false;
    std::string userDirection; 
    std::string userExit = "EXIT";
    //the maze has 8 rooms
    //8th room has exit
    //create necessary nodes
    RoomNode *head;
    head = new RoomNode("Beginning (Room 1)");
    RoomNode *secondRoom = new RoomNode("Room 2");
    RoomNode *thirdRoom = new RoomNode("Room 3");
    RoomNode *fourthRoom = new RoomNode("Room 4");
    RoomNode *fifthRoom = new RoomNode("Room 5");
    RoomNode *sixthRoom = new RoomNode("Room 6");
    RoomNode *seventhRoom = new RoomNode("Room 7");
    RoomNode *eighthRoom = new RoomNode("EXIT");

    //build linked list
    //RoomNode contructor defaults all directions to NULL
    head->east = secondRoom;
    secondRoom->south = thirdRoom;
    secondRoom->west = head;
    thirdRoom->west = fifthRoom;
    thirdRoom->east = fourthRoom; //fourth room is dead end
    thirdRoom->north = secondRoom;
    fifthRoom->north = head;
    fifthRoom->south = sixthRoom;
    sixthRoom->west = seventhRoom;
    seventhRoom->north = fourthRoom;
    seventhRoom->south = eighthRoom;

        std::cout << "You must navigate your way out of the maze." << std::endl;
        std::cout << "Do so by specifying the direction you would" << std::endl;
        std::cout << "like to travel (East, West, North, or South)." << std::endl;


    RoomNode *traverse = head; //point to beginning of list

    do
    {
        std::cout << "You are currently in room " << traverse-> label << std::endl;
        std::cout << "Enter the direction you wish to travel in (lowercase)." << std::endl;
        getline(std::cin, userDirection);

        if (userDirection != "east" || userDirection != "north" || 
            userDirection != "west" || userDirection != "south")
        {
            std::cout << "You did not enter a valid direction." << std::endl;
            std::cout << "Please try again, this time entering" << std::endl;
            std::cout << "north, east, west, or south." << std::endl;
            break;
        }
        else
        {
            if (userDirection == "west")
            {
                if (traverse->west == NULL)
                {
                    std::cout << "Sorry, the door in that direction is boarded shut!" << std::endl;
                    break;
                }
                else
                {
                    std::cout << "You moved " << userDirection << "!" << std::endl;
                    traverse = traverse->west; //update current position                    
                }

                if (traverse->label == userExit)
                {
                    std::cout << "You found the exit! Congratulations!" << std::endl;
                    std::cout << "You were able to escape the serpent!" << std::endl;
                    exitFound = true;
                    break;
                }   
            }
            else if (userDirection == "north")
            {
                if (traverse->north == NULL)
                {
                    std::cout << "Sorry, the door in that direction is boarded shut!" << std::endl;
                    break;                  
                }
                else
                {
                    std::cout << "You moved " << userDirection << "!" << std::endl;
                    traverse = traverse->north; 
                }

                if (traverse->label == userExit)
                {
                    std::cout << "You found the exit! Congratulations!" << std::endl;
                    std::cout << "You were able to escape the serpent!" << std::endl;
                    exitFound = true;
                    break;                  
                }
            }
            else if (userDirection == "east")
            {
                if (traverse->south == NULL)
                {
                    std::cout << "Sorry, the door in that direction is boarded shut!" << std::endl;
                    break;                  
                }
                else
                {
                    std::cout << "You moved " << userDirection << "!" << std::endl;
                    traverse = traverse->east; 
                }

                if (traverse->label == userExit)
                {
                    std::cout << "You found the exit! Congratulations!" << std::endl;
                    std::cout << "You were able to escape the serpent!" << std::endl;
                    exitFound = true;
                    break;                  
                }               
            }
            else if (userDirection == "south")
            {
                if (traverse->south == NULL)
                {
                    std::cout << "Sorry, the door in that direction is boarded shut!" << std::endl;
                    break;                  
                }
                else
                {
                    std::cout << "You moved " << userDirection << "!" << std::endl;
                    traverse = traverse->south; 
                }

                if (traverse->label == userExit)
                {
                    std::cout << "You found the exit! Congratulations!" << std::endl;
                    std::cout << "You were able to escape the serpent!" << std::endl;
                    exitFound = true;
                    break;                  
                }
            }
        }

    } while (exitFound);

    delete head;
    delete traverse;
    delete secondRoom;
    delete thirdRoom;
    delete fourthRoom;
    delete fifthRoom;
    delete sixthRoom;
    delete seventhRoom;
    delete eighthRoom;

    return 0;
}

我知道它可以缩短很多，但我的主要重点是让链表正常工作，有人可以帮我吗？谢谢

Answer 1

我发现遇到"delete traverse"会出现这种情况。 traverse 指向别的东西，而不是它自己的对象，在本例中是 head，它已经被删除了。

这就是它在输入后跳出循环的原因：

    if (userDirection != "east" || userDirection != "north" || 
        userDirection != "west" || userDirection != "south")

请考虑使用 && 而不是 ||，这样 userDirection 的有效值将导致表达式为 false 并且流程会落入 else 块以进行方向处理。

另外，exitFound为false，所以它可能会在第一次迭代后退出循环。也许 while 条件需要是 while (!exitFound).

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