C++书上例题分析总结

这是考试前总结的面向对象程序设计书上的例题，以及特殊函数和自己的分析；这是考试前总结的面向对象程序设计书上的例题，以及特殊函数和自己的分析；这是考试前总结的面向对象程序设计书上的例题，以及特殊函数和自己的分析

//函数重载 1.6

#include "iostream"
using namespace std;
int max(int a,int b){
    return a>b?a:b;
} 
float max(float a,float b){
    return a>b?a:b;
}
long max(long a,long b){
    return a>b?a:b;
}
int main(){
    int a,b;
    cin>>a>>b;
    cout<<max(a,b)<<endl;
    return 0;
}
//函数模板 1.8
//使用模板时不能只使用两个参数，会报错，如
//[Error] call of overloaded 'max(int&, int&)' is ambiguous
#include "iostream"
using namespace std;
template <typename T>
T max(T a,T b,T c){
    if(b>a) a=b;
    if(c>a) a=c;
    return a;
}
int main(){
    int i1=8,i2 = 5,i3 = 6,i;
    double d1 = 56.9,d2 = 90.765,d3 = 43.1 ,d;
    long g1 = 678435,g2 = -1555,g3 = 784354,g;
    i = max(i1,i2,i3);
    d = max(d1,d2,d3);
    g = max(g1,g2,g3);
    cout<<i<<endl;
    cout<<d<<endl;
    cout<<g<<endl;
    return 0;
}
//使用变量的引用来传递值进行转换，也可以传递地址，使用指针获取地址再使用
//变量的引用 1.12
#include "iostream"
using namespace std;
int swap(int &a,int &b){
    return a>b?a:b;
}
int main(){
​   
    int n,m;
    cin>>n>>m;
    cout<<swap(n,m);
    return 0;
}

//一个简单的类  2.4
#include "iostream"
#include "algorithm"
using namespace std;
class Array_max{
    public:
        void set_value();
        void max_value();
        void show_value();
    private:
        int array[100];
        int maxn;
}; 
void Array_max::set_value(){
    for(int i=0;i<10;i++){
        cin>>array[i];
    }
}
void Array_max::max_value(){
    sort(array,10);
    maxn = array[9];
}
void Array_max::show_value(){
    cout<<"max="<<maxn<<endl;
}
int main(){
    Array_max arr;
    arr.set_value();
    arr.max_value();
    arr.show_value();
    return 0;
}
简单的构造函数  3.1
#include "iostream"
using namespace std;
class Time{
    public:
        Time(){ hour = minute = sec = 0;}
        void set_time();
        void show_time();
    private:
        int hour;
        int minute;
        int sec;
};
void Time::set_time(){
    cin>>hour>>minute>>sec;
}
void Time::show_time(){
    cout<<hour<<":"<<minute<<":"<<sec<<endl;
}
int main(){
    Time t;
    t.show_time();
    return 0;
}
类外定义有参的构造函数  3.2
#include "iostream"
using namespace std;
class Time{
    public:
        Time(int,int,int);
        void set_time();
        void show_time();
    private:
        int hour;
        int minute;
        int sec;
};
void Time::set_time(){
    cin>>hour>>minute>>sec;
}
void Time::Time(int h,int m,int s){
     hour = h;
minute = m;
sec = s;
}
void Time::show_time(){
    cout<<hour<<":"<<minute<<":"<<sec<<endl;
}
int main(){
    Time t;
    t.show_time();
    return 0;
}

使用默认参数的构造函数  3.4
#include "iostream"
using namespace std;
class Box{
    public:
        Box(int h=0,int w=10,int len=10);
        int volume();
    private:
        int height;
        int width;
        int length;
};
Box::Box(int h,int w,int len){
    height = h;
    weigth = w;
    length = len;
}
int Box::volume(){
    return height*weigth*length;
}
int main(){
    Box box1;
    cout<<box1.volume()<<endl;
    Box box2(15);
    cout<<box2.volume()<<endl;
    Box box3(15,30);
    cout<<box3.volume()<<endl;
    Box box4(15,30,20);
    cout<<box4.volume()<<endl;
    return 0;
}
析构函数  3.5
#include "iostream"
#include "string"
using namespace std;
class Student{
    public:
        Student(int n,string nam,char s){
            num = n;
            name = nam;
            sex = s;
            cout<<"Constructor called."<<endl;
        }
        ~Student(){
            cout<<"Destructor called."<<endl;
        }
        void dispaly(){
            cout<<"num: "<<num<<endl;
            cout<<"name: "<<name<<endl;
            cout<<"sex: "<<sex<<endl;
        }
    private:
        int num;
        string name;
        char sex;
};
int main(){
​   
    Student stud1(10010,"Wang_li",'f');
    stud1.dispaly();
    Student stud2(10011,"Zhang_fan",'m');
    stud2.dispaly();
    return 0;
}

对象指针：
Time *pt;  定义指针
Time t1;   定义对象
pt = &t1;  将t1的起始地址给指针pt
指针对成员的引用
*pt
(*pt).hour
pt->hour
普通函数可以在类内声明为友元函数
friend void display(Time&);
其他类里的成员函数也可以在类内声明为友元函数
friend void Time::display(Date&)
注意括号里的内容，友元函数可以访问私有成员

最开始的复数相加，重载+运算符  4.2
其他符号的重载都相似，会一个就行
#include "iostream"
using namespace std;
class Complex{
    public:
        Complex(){real = 0;imag = 0;}
        Complex(double r,double i){real = r;imag = i;}
        Complex operator +(Complex &c2);
        void display();
    private:
        double real;
        double imag;
};
Complex Complex::operator +(Complex &c2){
    Complex c;
    c.real = real + c2.real;
    c.imag = imag + c2.imag;
    return c; 
}
void Complex::display(){
    cout<<real<<" : "<<imag<<endl;
}
int main(){
    Complex c1(3,4),c2(5,-10),c3;
    c3 = c2 + c1;
    c3.display(); 
    return 0;
}

重载流插入运算符和流提取运算符
istream & operator >>(istream &,自定义类 &);
ostream & operator <<(ostream &,自定义类 &);
重载流插入运算符 《
#include "iostream"
using namespace std;
class Complex{
    public:
        Complex() {real = 0;imag = 0;}
        Complex(double r,double i){real = r;imag = i;}
        Complex operator +(Complex&c2);
        friend ostream& operator <<(ostream,Complex&);
    private:
        double real;
        double imag;
};
Complex Complex::operator +(Complex&c2){
    return Complex(real+c2.real,imag+c2.imag);
}
ostream & operator <<(ostream & output,Complex&c){
    output<<"("<<c.real<<"+"<<c.imag<<"i)"<<endl;
    return output;
}
int main(){
    Complex c1(2,4),c2(6,10),c3;
    c3 = c2 + c1;
    cout<<c3<<endl; 
    return 0;
}


重载流提取运算符
#include "iostream"
using namespace std;
class Complex{
    public:
        friend ostream& operator <<(ostream&,Complex&);
        friend istream& operator >>(istream&,Complex&);
    private:
        double real;
        double imag;
};
ostream& operator <<(ostream& output,Complex& c){
    output<<c.real<<c.imag<<endl;
    return output;
}
istream& operator >>(istream& input,Complex& c){
    input>>c.real>>c.imag;
    return input;
}
int main(){
    Complex c1,c2;
    cin>>c1>>c2;
    cout<<c1<<endl;
    cout<<c2<<endl;
    return 0;
}