P200 7

<img src="https://img-blog.youkuaiyun.com/20150518130711865?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvWXVTb25nNDg2OQ==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" alt="" />#include <iostream> 
using namespace std; 
class A 
{  public:  
A(){a=0;b=0;} 
A(int i){a=i;b=0;} 
A(int i,int j){a=i;b=j;}  
void display(){cout<<"a="<<a<<" b="<<b;} 
private: 
int a; 
int b;  
}; 
class B : public A 
{  public: 
B(){c=0;}  
B(int i):A(i){c=0;}  
B(int i,int j):A(i,j){c=0;} 
B(int i,int j,int k):A(i,j){c=k;} 
void display1() 
{display();  
cout<<" c="<<c<<endl; 
}  
private: 
int c; 
}; 
int main() 
{ B b1; 
B b2(1); 
B b3(1,3); 
B b4(1,3,5); 
b1.display1();  
b2.display1(); 
b3.display1(); 
b4.display1(); 
return 0; 
}