《C++语言基础》程序阅读——指针、const、static

返回：贺老师课程教学链接

本周再补充三个和指针有关的阅读程序，进一步掌握指针工作的原理。
友情提醒：画出内存，让程序的分析，在理性、有序中完成。如果有时间的变化，博客中加个自己画的图。
可以在上机时通过单步执行，进一步和你在人脑中运行程序的过程进行对照。

(1) 阅读程序，写出程序的运行结果并理解

#include <iostream>
using namespace std;
class base
{
private:
    int m;
public:
    base() {};
    base(int m){this->m=m;}
    int get(){return m;}
    void set(int m){this->m=m;}
};//base_end 

int main()
{
    base *ptr;
    ptr=new base[2];
    ptr->set(30);
    ptr=ptr+1;
    ptr->set(50);
    base a[2]= {1,9};
    cout<<a[0].get()<<","<<a[1].get()<<endl;
    cout<<ptr->get()<<",";
    ptr=ptr-1;
    cout<<ptr->get()<<endl;
    delete[] ptr;
    return 0;
}

(2) 阅读程序，写出程序的运行结果并理解

#include<iostream>
using namespace std;
class CE
{
private:
    int a,b;
    int getmin(){return (a<b? a:b);}
public:
    int c;
    void SetValue(int x1,int x2, int x3)
    {
        a=x1;
        b=x2;
        c=x3;
    }
    int GetMin();
};

int CE::GetMin()
{
    int d=getmin();
    return (d<c? d:c);
}

int main()
{
    int x=5,y=12,z=8;
    CE *ep;
    ep=new CE;
    ep->SetValue(x+y,y-z,10);
    cout<<ep->GetMin()<<endl;
    CE a=*ep;
    cout<<a.GetMin()*3+15<<endl;
    return 0;
}

(3) 阅读程序，写出程序的运行结果并理解

#include <iostream>
using namespace std;
class Time
{
public:
    Time(int,int,int);
    void output_time( );
    int hour;
    int minute;
    int sec;
};

Time::Time(int h,int m,int s)
{
    hour=h;
    minute=m;
    sec=s;
}

void Time::output_time( )
{
    cout<<hour<<":";
    cout<<minute<<":" <<sec<<endl;
}

int main( )
{
    Time t1(10,13,56);
    int *p1=&t1.hour; //指向数据成员的指针
    cout<<*p1<<endl;
    t1.output_time( );

    Time *p2=&t1; //指向对象的指针
    p2->output_time( );

    void (Time::*p3)( ); //指向成员函数的指针
    p3=&Time::output_time;
    (t1.*p3)( );
    return 0;
}

(4) 请写出程序中const出现的语法现象及其所起的作用

#include <iostream>
#include <string>
using namespace std;
class Student
{
public:
    Student() {}
    Student( const string& nm, int sc = 0 ): name(nm), score(sc){}
    //（1）下面的const干神马？_____________
    void set_student( const string& nm, int sc = 0 )
    {
        name = nm;
        score = sc;
}

    //（2）下面的const分别干神马？___________
    const string& get_name() const
    {
        return name;
}

    int get_score() const
    {
        return score;
    }
private:
    string name;
    int score;
};

//（3）下面的const干神马？_____________
void output_student(const Student& student )
{
    cout << student.get_name() << "\t";
    cout << student.get_score() << endl;
}

int main()
{
    Student stu( "Wang", 85 );
    output_student( stu );
    return 0;
}

(5) 请写出下面程序的输出结果

#include<iostream>
using namespace std;
class myClass
{
public:
    myClass(){ number++;}
    ~myClass(){ number--;}
    static int number;
};

int myClass::number=0;

int main()
{
    myClass *ptr;
    myClass A,B;
    myClass *ptr_Arr=new myClass[3];
    ptr=ptr_Arr;
    myClass C;
    cout<<myClass::number<<endl;
    delete []ptr;
    return 0;
}

(6) 请写出下面程序的输出结果

#include <iostream>
using namespace std;
class Test{
   private:
      static int val;
      int a;
   public:
      static int func();
      static void sfunc(Test &r);
}; 

int Test::val=20;
int Test::func()
{
   val+=val;
   return val;
}

void Test::sfunc (Test &r)
{
    r.a=25;
    cout<<"Result3="<<r.a<<endl;
}

int main(){
  cout <<"Resultl="<<Test::func()<<endl;
  Test a;
  cout<<"Result2="<<a.func()<<endl;
  Test::sfunc (a);
  return 0;
}