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