4.20

 1 #include<iostream>
 2 using namespace std;
 3 int main()
 4 {
 5     int N,a,b,c,i,n,sum=0;
 6     cin>>N;cout<<endl;
 7     
 8     for(i=0;i<N;i++)
 9     {
10         cin>>a>>b;cout<<endl;
11     
12         sum+=b;
13     }
14 
15     c=sum/N;
16     cout<<c<<endl;
17 
18     
19 }

 1 #include<iostream>
 2 using namespace std;
 3 class Mammal
 4 {
 5 private:
 6     int itsAge;
 7     int itsWeight;    
 8 public:
 9     Mammal(int a,int b)
10     {
11         itsAge=a;
12         itsWeight=b;
13     }
14     void setweight(int weight)
15     {
16         itsWeight=weight;
17     }
18     void getweight()
19     {
20         cout<<itsWeight<<endl;
21     }
22     void getage()
23     {
24         cout<<itsAge<<endl;
25     }
26 };
27 class Dog:public Mammal
28 {
29 private:
30     int pinzhong;
31 public:
32     Dog(int a,int b,int c):Mammal(a,b)
33     {
34         pinzhong=c;
35     }
36     void getpinzhong()
37     {
38         cout<<pinzhong<<endl;
39     }
40     void yuyan()
41     {
42         cout<<"wangwangwang"<<endl;
43         Mammal::getweight();
44         Mammal::getage();
45     }
46 };
47 int main()
48 {
49     Dog d(1,10,2);
50     cout<<"年龄：";
51     d.getage();
52     cout<<"体重：";
53     d.getweight();
54     cout<<"品种：";
55     d.getpinzhong();
56     d.yuyan();
57 }

 1 #include<iostream>
 2 using namespace std;
 3 class Base0{
 4 public:
 5     int var0;
 6     void fun0(){cout<<"Member of Base0"<<endl;
 7     }
 8 };
 9 class Base1:public Base0{
10 public:
11     int var1;
12 };
13 class Base2:public Base0{
14 public:int var2;
15 };
16 class Derived:public Base1,public Base2{
17 public:
18     int var;
19     void fun(){
20         cout<<"Member of Derived"<<endl;}
21 };
22 int main()
23 {
24     Derived d;
25     d.Base1::var0=2;
26     d.Base1::fun0();
27     d.Base2::var0=3;
28     d.Base2::fun0();
29     return 0;
30 }
31  
32 
33 #include<iostream>
34 using namespace std;
35 class Base1{
36 public:
37         int var;
38     void fun(){cout<<"Member of Base1"<<endl;}
39 };
40 class Base2{
41 public:
42     int var;
43     void fun(){cout<<"Member of Base2"<<endl;}
44 };
45 class Derived:public Base1,public Base2{
46 public:
47     int var;
48     void fun(){cout<<"Member of Derived"<<endl;}
49 };
50 int main()
51 {
52     Derived d;
53     Derived*p=&d;
54     d.var=1;