C++第三章

4.#include <iostream> using namespace std; class Student  {public:     Student(int n,float s):num(n),score(s){}    void display();   private:    int num;     float score;  };   void Student::display()   {cout<<num<<" "<<score<<endl;}   int main()  {Student stud[5]={    Student(101,78.5),Student(102,85.5),Student(103,98.5),   Student(104,100.0),Student(105,95.5)};  Student *p=stud;   for(int i=0;i<=2;p=p+2,i++)   p->display();   return 0;} 

5.#include <iostream> using namespace std; class Student  {public:     Student(int n,float s):num(n),score(s){}    int num;    float score;}; int main()  {Student stud[5]={    Student(101,78.5),Student(102,85.5),Student(103,98.5),Student(104,100.0),Student(105,95.5)};  int  max(Student* );  Student *p=&stud[0];  max(p);  }    int max(Student *arr)   {  float max_score=arr[0].score;    int k=0;      for(int i=1;i<5;i++)        if(arr[i].score>max_score)    {max_score=arr[i].score;k=i;}     cout<<arr[k].num<<" "<<max_score<<endl;      return 0;} 

6-126:#include <iostream>using namespace std;class Student{public:   Student(int n,float s):num(n),score(s){}   void change(int n,float s) {num=n;score=s;}   void display(){cout<<num<<" "<<score<<endl;}  private:   int num;   float score; };int main(){Student stud(101,78.5); stud.display(); stud.change(101,80.5); stud.display(); return 0;}7: 解法一#include <iostream>using namespace std;class Student {public:   Student(int n,float s):num(n),score(s){}   void change(int n,float s) {num=n;score=s;}   void display() {cout<<num<<" "<<score<<endl;}     //可改为:void display() const {cout<<num<<" "<<score<<endl;}  private:   int num;   float score; };int main(){const Studentstud(101,78.5); stud.display(); //stud.change(101,80.5); stud.display(); return 0;}解法二：#include <iostream>using namespace std;class Student {public:   Student(int n,float s):num(n),score(s){}   void change(int n,float s) const  {num=n;score=s;}   void display() const {cout<<num<<" "<<score<<endl;}  private:   mutable int num;   mutable float score; };int main(){const Student stud(101,78.5); stud.display(); stud.change(101,80.5); stud.display(); return 0;}解法三：#include <iostream>using namespace std;class Student {public:   Student(int n,float s):num(n),score(s){}   void change(int n,float s) {num=n;score=s;}   void display() {cout<<num<<" "<<score<<endl;}  private:   int num;   float score; };int main(){Student stud(101,78.5); Student *p=&stud; p->display(); p->change(101,80.5); p->display(); return 0;}8：#include <iostream>using namespace std;class Student {public:   Student(int n,float s):num(n),score(s){}   void change(int n,float s) {num=n;score=s;}   void display() {cout<<num<<" "<<score<<endl;}  private:   int num;   float score; };int main(){Student stud(101,78.5); void fun(Student&); fun(stud); return 0; }void fun(Student &stu){stu.display();stu.change(101,80.5); stu.display();}9：#include <iostream>using namespace std;class Product {public:   Product(int n,int q,float p):num(n),quantity(q),price(p){};   void total();   static float average();   static void display();  private:   int num;   int quantity;   float price;   static float discount;   static float sum;   static int n; };void Product::total() {float rate=1.0;  if(quantity>10) rate=0.98*rate;  sum=sum+quantity*price*rate*(1-discount);  n=n+quantity; }void Product::display() {cout<<sum<<endl;  cout<<average()<<endl; }float Product::average() {return(sum/n);}float Product::discount=0.05;float Product::sum=0;int Product::n=0;int main() {   Product Prod[3]={     Product(101,5,23.5),Product(102,12,24.56),Product(103,100,21.5)    };   for(int i=0;i<3;i++)     Prod[i].total();   Product::display();   return 0; } 10：#include <iostream>using namespace std;class Date;class Time {public:   Time(int,int,int);   friend void display(const Date &,const Time &);  private:   int hour;   int minute;   int sec; }; Time::Time(int h,int m,int s) {hour=h;  minute=m;  sec=s; }class Date {public:Date(int,int,int);   friend void display(const Date &,const Time &);  private:   int month;   int day;   int year; };Date::Date(int m,int d,int y) {month=m;  day=d;  year=y; }void display(const Date &d,const Time &t) {  cout<<d.month<<"/"<<d.day<<"/"<<d.year<<endl;  cout<<t.hour<<":"<<t.minute<<":"<<t.sec<<endl; }int main(){ Time t1(10,13,56); Date d1(12,25,2004); display(d1,t1); return 0;} 11：#include <iostream>using namespace std;class Time;class Date {public:   Date(int,int,int);   friend Time;private:   int month;   int day;   int year; };Date::Date(int m,int d,int y):month(m),day(d),year(y){ }class Time {public:   Time(int,int,int);   void display(const Date &);  private:   int hour;   int minute;   int sec; };Time::Time(int h,int m,int s):hour(h),minute(m),sec(s){ }void Time::display(const Date &d) {  cout<<d.month<<"/"<<d.day<<"/"<<d.year<<endl;  cout<<hour<<":"<<minute<<":"<<sec<<endl; }int main(){ Time t1(10,13,56); Date d1(12,25,2004); t1.display(d1); return 0;}12：#include <iostream>using namespace std;template<class numtype>class Compare {public:   Compare(numtype a,numtype b);   numtype max();   numtype min();  private:   numtype x,y; };template <class numtype>Compare<numtype>::Compare(numtype a,numtype b)  {x=a;y=b;}template <class numtype>numtype Compare<numtype>::max() {return (x>y)?x:y;}template <class numtype>numtype Compare<numtype>::min()  {return (x<y)?x:y;}int main(){Compare<int> cmp1(3,7); cout<<cmp1.max()<<" is the Maximum of two integer numbers."<<endl; cout<<cmp1.min()<<" is the Minimum of two integer numbers."<<endl<<endl; Compare<float> cmp2(45.78,93.6); cout<<cmp2.max()<<" is the Maximum of two float numbers."<<endl;cout<<cmp2.min()<<" is the Minimum of two float numbers."<<endl<<endl; Compare<char> cmp3('a','A'); cout<<cmp3.max()<<" is the Maximum of two characters."<<endl; cout<<cmp3.min()<<" is the Minimum of two characters."<<endl; return 0;}