17.电话号码的组合

来源于题解思路： 

继承

CC14 KiKi设计类继承

#include <iostream>
#include <memory>
using namespace std;
class Shape{
private:
    int x;
    int y;
};

class Rectangle:public Shape
{
public:
    Rectangle(int length,int width)
        :Shape()
        ,_length(length)
        ,_width(width)
        {}
    void GetArea()
    {
        cout<<_length*_width<<endl;
    }
protected:
    int _length;
    int _width;
};
class Circle:public Shape{
public:
    Circle(int r)
        :Shape()
        ,_r(r)
        {}
    void GetArea()
    {
        cout<<3.14*_r*_r<<endl;
    }
private:
    int _r;
};
class Square:public Rectangle
{
public:
    Square(int len)
        :Rectangle(len,len)
        {}
    void GetArea()
    {
        cout<<_length*_length<<endl;
    }

};
int main() {
    int length=0,width=0;
    cin>>length>>width;
   Rectangle ret(length,width);
   ret.GetArea();
   int r;
   cin>>r;
   Circle cir(r);
   cir.GetArea();

   int len;
   cin>>len;
   Square le(len);
   le.GetArea();
}
// 64 位输出请用 printf("%lld")

 双指针算法

283.移动零