C++重点和练习

 作业题目：

#include <iostream>
using namespace std;
class Rec
{const int length;int width;
public:void set_length(int l);void set_width(int w);int get_length();int get_width();void show();
};#include <iostream>
using namespace std;
class Cir
{int &r;
public:void set_r(int r);  //设置私有属性r的值void show(double PI=3.14);   //参数有默认值3.14
};#include <iostream>
using namespace std;
class Car  //类名首字母一般大小
{string color;string brand;int speed;
public:void set(string c,string b,int s);void display();void acc(int a);
};

答案：

#include <iostream>using namespace std;class Rectangle
{const int length;int width;
public:
//    void set_length(int len);Rectangle(int length):length(length){}void set_width(int wid);int get_length();int get_width();void show();
};//Rectangle R3;
//void Rectangle::set_length(int len)
//{
//   length = len;
//}void Rectangle::set_width(int width)
{this->width = width;
}int Rectangle::get_length()
{return length;
}
int Rectangle::get_width()
{return width;
}
void Rectangle::show()
{cout << this << endl;int s = 2*(width+length);int area = width*length;cout << "周长：" << s << "\t"<< "面积：" << area << endl;
}class Circle
{int &r;
public:Circle(int &r1):r(r1){}void set_r(int tr);void show(float PI = 3.14);
};void Circle::set_r(int tr)
{r = tr;
}
void Circle::show(float PI)
{float s = PI*2*r;float area = PI*r*r;cout << "周长：" << s << "\t"<< "面积：" << area << endl;
}class Car
{string color;string brand;float speed;
public:Car():color("red"),brand("玛莎拉蒂"),speed(360){}void display();void acc(int a);void set_color(string c);void set_brand(string b);void set_speed(float s);};void Car::display()
{cout << "颜色：" << color << "\t"<< "品牌：" << brand << "\t"<< "速度：" << speed<< endl;
}
void Car::set_color(string c)
{color = c;
}
void Car::set_brand(string b)
{brand = b;
}
void Car::set_speed(float s)
{speed = s;
}
void Car::acc(int a)
{speed += a;
}int main()
{Rectangle rec1(3);rec1.set_width(3);cout << "rec1长度：" << rec1.get_length() << "\t"<< "rec1宽度：" << rec1.get_width()  <<endl;rec1.show();int r = 1;Circle r1(r);r1.show();r1.set_r(2);r1.show();Car car1;car1.display();car1.set_color("red");car1.set_brand("奥迪");car1.set_speed(240);car1.display();car1.acc(5);car1.display();return 0;
}

自己定义构造函数：

#include <iostream>
#include <cstdlib>
using namespace std;
class Stu
{int age;double score;
public://Stu(){cout << "Stu的无参构造" << endl;}//实现Stu的有参构造Stu(int age,double score){this->age = age;this->score = score;cout << "Stu的有参构造" << endl;}void show();
};
void Stu::show()
{cout << "age = " << age << endl;cout << "score = " << score << endl;
}
int main()
{//Stu s1;//Stu *p1 = (Stu*)malloc(sizeof(Stu));Stu *p1;cout << "*********" << endl;p1 = new Stu(1,3.14);  // new Stu{1,3.14}也可以  //类中只提供了有参构造，所以new申请空间时必须给初始值可以用{},也可以用()p1->show();//Stu s1(12,31.9);   //调用了有参构造return 0;
}

参数和成员属性同名：

#include <iostream>
#include <cstdlib>
using namespace std;
class Stu
{int age;double score;
public:Stu(int age,double score):age(age),score(score){cout << "Stu有两个参数的有参构造" << endl;}void show();
};
void Stu::show()
{cout << "age = " << age << endl;cout << "score = " << score << endl;
}
int main()
{Stu s2(12,31.9);s2.show();return 0;
}

类中存在引用成员时：
 

#include <iostream>
#include <cstdlib>
using namespace std;
class Stu
{int &age;double score;
public:Stu(int &age,double score):age(age),score(score){cout << "Stu有两个参数的有参构造" << endl;}void show();void set_age(){age=0;}
};
void Stu::show()
{cout << "age = " << age << endl;cout << "score = " << score << endl;
}
int main()
{int age = 18;Stu s2(age,31.9);s2.show();s2.set_age();cout << age << endl;  //局部变量age的值为0，因为类对象中的age引用了该局部变量return 0;
}

类中存在const修饰的成员时：
 

#include <iostream>
#include <cstdlib>
using namespace std;
class Stu
{const int age;double score;
public://Stu():age(23){cout << "Stu的无参构造" << endl;}//实现Stu的有参构造Stu(int age,double score):age(age),score(score){cout << "Stu有两个参数的有参构造" << endl;}Stu(int age):age(age){cout << "Stu有一个参数age的有参构造" << endl;}/*Stu(double score):age(20){this->score = score;cout << "Stu有一个参数score的有参构造" << endl;}*/void show();
};
void Stu::show()
{cout << "age = " << age << endl;cout << "score = " << score << endl;
}
int main()
{int age = 18;Stu s2(age,31.9);s2.show();Stu s1(24);s1.show();return 0;
}

类中存在其他类对象时：

#include <iostream>
using namespace std;
class Stu
{int age;float score;
public:Stu(int age,float score):age(age),score(score){}int get_age(){return age;}double get_score(){return score;}
};
class Person
{const int id;const string name;Stu stu1;
public:Person(int id,string name,Stu stu1):id(id),name(name),stu1(stu1){}Person(int id,string name,int age,float score):id(id),name(name),stu1(age,score){}void show(){cout << "id = " << id << "\t"<< "name = " << name << "\t"<< "age = " << stu1.get_age() << "\t"<< "score = " << stu1.get_score() << endl;}
};int main()
{Stu stu1(18,99.9);Person p1(10086,"张三",stu1);p1.show();Person p2(10085,"李四",19,88.8);p2.show();return 0;
}