代码实现：

#include<iostream>
using namespace std;

//基类
class COperation {
	public:
		int m_nFirst;
		int m_nSecond;
		virtual double GetResult()
		{
			double dResult=0;
			return dResult;
		}
};
//加法
class AddOperation:public COperation
{
	public:
		virtual double GetResult()
		{
			return m_nFirst+m_nSecond;
		}
};
//减法
class SubOperation:public COperation {
	public:
		virtual double GetResult()
		{
			return m_nFirst-m_nSecond;
		}
};
//工厂类
class CCalculatorFactory {
	public:
		static COperation* Create(char cOperator);
};

COperation* CCalculatorFactory::Create(char cOperator)
{
	COperation* oper;
	switch(cOperator)
	{
		case'+':
			oper=new AddOperation();
			break;
		case'-':
			oper=new SubOperation();
			break;
		default:
			oper=new AddOperation();
			break;
	}
	return oper;
}
//客户端
int main()
{
	int a,b;
	cout<<"请输入两个操作数，空格分开："<<endl;
	cin>>a>>b;
	COperation* op=CCalculatorFactory::Create('-');
	op->m_nFirst=a;
	op->m_nSecond=b;
	cout<<op->GetResult()<<endl;
	
	return 0;
}

C++简单工厂模式