C++涉及抽象类、多态、虚函数和纯虚函数实现的计算器出现停止工作

Question

Dev c++环境下运行的c++代码。编译运行时显示“已停止工作”。

#include<iostream>
using namespace std;

//计算器
class Calculator
{
public:
    void setA(int a)
    {
        this->mA=a;
    }
    void setB(int b)
    {
        this->mB=b;
    }
    void setOperator(string oper)
    {
        this->mOperator = oper;
    }
    int getResult()
    {
        if(this->mOperator == "+")
        {
            return mA+mB; 
        }
        else if(this->mOperator == "-")
        {
            return mA-mB;
        }
        else if(this->mOperator == "*")
        {
            return mA*mB;
        }
        else if(this->mOperator == "/")
        {
            return mA/mB;
        }
    }
private:
    int mA;
    int mB;
    string mOperator;
}; 

//这种程序不利于扩展，维护困难，如果修改功能或者扩展功能需要在 源代码基础上修改
//面向对象程序设计一个基本原则:开闭原则（对修改关闭，对扩展开放）

//抽象基类
class AbstractCalculator
{
public:
    void setA(int a)
    {
        this->mA = a;
    }
    virtual void setB(int b)
    {
        this->mB=b;
    }
    virtual int getResult()=0;
    
protected:
    int mA;
    int mB;
    string mOperator;
}; 

//加法计算器
class PlusCalculator:public AbstractCalculator
{
public:
    virtual int getResult()
    {
        return mA+mB;
    }
};

//减法计算器
class MinusCalculator:public AbstractCalculator
{
public:
    virtual int getResult()
    {
        return mA-mB;
    }
};

//乘法计算器
class MultipliesCalculator:public AbstractCalculator
{
public:
    virtual int getResult()
    {
        return mA*mB;    
    }
}; 

void DoBusiness(AbstractCalculator* calculator)
{
    int a =10;
    int b =20;
    calculator->setA(a);
    calculator->setB(b);
    cout<<"计算结果:"<<calculator->getResult()<<endl;
    delete calculator;
}

int main()
{
    AbstractCalculator* ac;
    DoBusiness(ac);
    
    return 0;
}

Answer 1

问题呢
又一个把这里当博客分享代码的吗