The third pre class exercise

One 、 Single topic selection

2-1
Given the following class declaration , Which member function may change the member variable data?（D）

class A {

public:

void f1 (int d);
void f2 (const int &d);
void f3 (int d) const;
private:

int data;
};

A.f1
B.f2
C.f3
D.f1 and f2

2-2
In the following keywords , Used to describe the public members of a class is （A ）.

A.public
B.private
C.protected
D.friend

2-3
The following incorrect statements about classes and objects are （ C）.

A. Object is an instance of a class
B. Any object can only belong to a specific class
C. A class can only have one object
D. The relationship between classes and objects is similar to that between data types and variables

2-4
The default access property of class members is ：（A）

A.private
B.protected
C.public
D. None of the above answers is true

2-5
In object-oriented software systems , A construction of communication between objects of different classes is called ___D____.

A. attribute
B. encapsulation
C. class
D. news

Two 、 Completion

1.（6 branch ）A class is a user-defined type A class consists of a set of members. The most common kinds of members are data members and member functions A class is a namespace containing its members.

2.（6 branch ）C++ classes are a tool for creating new types that can be used as conveniently as the built-in types The fundamental idea in defining a new type is to separate the incidental details of the implementation(e.g., the layout of the data used to store an object of the type) from the properties essential to the correct use of it (e.g., the complete list of functions that can access the data). Such a separation is best expressed by channeling all uses of the data structure and its internal housekeeping routines through a specific interface

3、 ... and 、 Function questions

6-1 Design a project called Rectangle Rectangle class （C++ set function ）

fraction 10
author Zhang Dehui
Company Xi'an University of Posts and Telecommunications
Design a project called Rectangle Rectangle class , This class includes ： Two are called width and height Of double Data fields , They represent the width and height of the rectangle, respectively . One for width and height The function that sets the initial value set( ); A group called getArea( ) Function that returns the area of a rectangle ; A group called getPerimeter( ) The function of returns the perimeter of the rectangle . Please implement this class .

Class called ：
Rectangle
Sample referee test procedure ：
Here is an example of a function being called for testing . for example ：
#include
using namespace std;
// The code you submit will be embedded here

int main()
{
double m,n;
cin>>m;
cin>>n;
Rectangle a;
a.set(m,n);
cout<<a.getArea()<<endl;
cout<<a.getPerimeter()<<endl;
return 0;
}
sample input ：
3.5 35.9
sample output ：
125.65
78.8

class Rectangle
{
    
	private:
		double width;
		double height;
	public:
        void set(double m,double n)
        {
    
            width=m;
			height=n;
        }
    
		double getArea()
		{
    
			double area;
			area=width*height;
			return area;
		}
    
		double getPerimeter()
		{
    
			double perimeter;
			perimeter=2*(width+height);
			return perimeter;
		}
};
 

6-2 Point Class declaration and Implementation

fraction 10
author Li Tingyuan
Company China Academy of Civil Aviation
Define a Point class , Represents a point on the plane , Its abscissa and ordinate are respectively in x and y Express , Design Point class , Implement and test this class .
Enter the coordinates of the two points in the main function , Calculate and output the distance between two points . Please implement according to the main function Point class .

Sample referee test procedure ：
#include
#include
#include
using namespace std;

// Your code will be embedded here

int main()
{
Point p1, p2;
double x1, y1, x2, y2;
cin >> x1 >> y1 >> x2 >> y2;
p1.setX(x1);
p1.setY(y1);
p2.setX(x2);
p2.setY(y2);
double x = p1.getX() - p2.getX();
double y = p1.getY() - p2.getY();
double len = sqrt(x * x + y * y);
cout << fixed << setprecision(2) << len << endl;
return 0;
}
sample input ：
0 0 3 3
sample output ：
4.24

class Point 
{
    
    private:
        int x, y;
    public:
        void setX(double x1) {
     x = x1; }
        void setY(double y1) {
     y = y1; }
        double getX() {
     return x; }
        double getY() {
     return y; }
};