Question

我必须创建一个具有子类的Shape，用于查找体积的特定形状。我们必须能够构造对象并将它们存储在链表中。我正在测试创建一个对象，我想知道它为什么不运行我的函数cout命令。任何帮助将不胜感激。感谢

#include <iostream>
#include <array>

using namespace std;

class Shape{
public:
    friend class my_list;
    Shape(double a=0,double b=0 ,double c=0):width(a),height(b),length(c){
    }

protected:
    double width;
    double height;
    double length;
    Shape *nextPtr;
};

class Rectangle:public Shape
{
public:
    Rectangle(double a, double b,double c):Shape(a,b,c){
        area = width * length;
    };

private:
    double area;
};

class Circle:public Shape
{
public:
    Circle(double a):Shape(a){
        area = (radius*radius)*3.14;
    }
protected:
    double area;
    double radius;
};

class Triangle:public Shape
{
public:
    Triangle(double a, double b,double c):Shape(a,b,c){
        area = .5*width*length;
    };
protected:
    double area;
};

class Cubic:public Rectangle
{
public:
    Cubic(double a, double b,double c):Rectangle(a,b,c){
        volume = width * length * height;
    };
protected:
    double volume;
};

class Sphere:public Circle
{
public:
    Sphere(double a):Circle(a){
        volume = (width*width*width)*(4/3)*3.14;
    };
protected:
    double volume;
};

class Cone:public Circle{
public:
    Cone(double a, double b):Circle(a){
        height = b;
        volume = 3.14*(width*width)*(height/3);
    };
protected:
    double volume;
};

class my_list{
public:
    my_list();
    ~my_list();

    void add_node(Shape*);
    void print_list();
    Shape* make_node();

private:
    Shape* firstPtr;
    Shape* lastPtr;
};

my_list::my_list():firstPtr(NULL), lastPtr(NULL){}
my_list::~my_list(){}

Shape* my_list::make_node(){
    cout << "What shape would you like to construct?" << endl;
    cout << "\t1. Rectangle" << "\n\t2. Triangle" << "\n\t3. Cirlce" <<
    "\n\t4. Cubic" <<"\n\t5. Sphere" << "\n\t6. Cone" << endl;
    int number; cin >> number; cin.get();

    cout << "Enter width/height/length or radius, or radius/height" << endl;
    double a,b,c; cin >> a; cin>>b; cin>> c;
    switch (number) {
        case 1: {
            Shape *newPtr = new Rectangle(a,b,c);
            return newPtr;
        }

        case 2: {
            Shape *newPtr = new Triangle(a,b,c);
            return newPtr;

        }

        case 3: {
            Shape *newPtr = new Circle(a);
            return newPtr;
        }
        case 4: {
            Shape *newPtr = new Sphere(a);
            return newPtr;
        }
        case 5: {
            Shape *newPtr = new Cubic(a,b,c);
            return newPtr;
        }

        case 6:{
            Shape *newPtr = new Cone(a,b);
            return newPtr;
        }
        default:
               return 0;
    }
}

void my_list::add_node(Shape* new_node){
    if ( firstPtr == NULL ) // empty list
        firstPtr = lastPtr = new_node; // nextPtr  = NULL by default
    else {
        new_node -> nextPtr = firstPtr;
        firstPtr = new_node; // set first pointer to beginning of the list;
    }
}

int main(){
    /*
    while(true) {
        cout << endl << endl << "\tSelect the following options" << endl;
        cout << "\t1. Construct" << "\n\t2. Add" << "\n\t3. Print" <<
        "\n\t4. Quit" << endl;
        cout << "\tSelection:\t";
        int options; cin >> options; cin.get(); // cin leaves newline, cin.get() to cancel it

        switch (options) {
            case 1: //construct function

            case 2: {
              //add function
            }

            case 3:
               //print function



            case 4:
            default: break;
        }
    }
    */

    my_list l1;
    l1.add_node(l1.make_node());
}

Answer 1

指点：

在调用my_list上的任何函数之前尝试创建它的对象。比如my_list l1 = new my_list（）;
在switch-case使用中使用break而不是return。喜欢：

switch（n）{ 情况1： ... 打破;

案例2： ... 打破; }

3.启动IDE并添加断点进行调试。

C ++链表/多态无法运行列表功能

1 个答案: