C++ Primer Plus第六版编程题（第7章）
题目
1.编写一个程序，不断要求用户输入两个数，直到其中的一个为0。对于每两个数，程序将使用一个函数来计算它们的调和平均数，并将结果返回给main（），而后者将报告结果。调和平均数指的是倒数平均值的倒数，计算公式如下:
调和平均数=2.0xy/(x+y)
2.编写一个程序，要求用户输入最多10个高尔夫成绩，并将其存储在一个数组中。 程序允许用户提早结束输入，并在一行上显示所有成绩，然后报告平均成绩。请使用3个数组处理函数来分别进行输入、显示和计算平均成绩。
3.下面是一个结构声明：
struct box
{
char maker[40];
float height;
float width;
float length;
float volume;
};
a.编写一个函数，按值传递box结构，并显示每个成员的值。
b.编写一个函数，传递box结构的地址，并将volume成员设置为其他三维长度的乘积。
c.编写一个使用这两个函数的简单程序。
4.许多州的**发行机构都使用如程序清单7.4所示的简单**玩法的变休。在这些玩法中，玩家从一组被称为城号码 (field mumber)的号码中选择几个。例如，可以从域号码1~47中选择5个号码；还可以从第二个区间（如1-27)选择一个号码(称为特选号码)。要赢得头奖，必须正确猜中所有的号码。中头奖的几率是选中所有域号码的儿率与选中特选号码几率的乘积。例如，在这个例子中，中头奖的几率是从47个号码中正确选取5个号码的几率与从27个号码中正确选择1个号码的几率的乘积。请修改程字请单7.4,以计算中得这种**头奖的几率。
5.定义一个递归函数，接受一个整数参数，并返回该参数的阶乘。前面讲过，3的阶乘写作3!。等于3 * 2!, 依此类推；而0被定义为1。通用的计算公式是，如果n大于零，则n！=n* (n-1)！.在程序中对该函数进行测试，程序使用循环让用户输入不同的值，程序将报告这些值的阶乘。
程序
7.1
#include <iostream>
using namespace std;
double average(double a,double b);
int main()
{
double a,b,m;
cout<<"Please input two numbers: ";
cin>>a>>b;
while(a!=0&&b!=0)
{
m=average(a,b);
cout<<"The average is: "<<m<<endl;
cout<<"Please input two numbers: ";
cin>>a>>b;
}
cout<<"Done."<<endl;
return 0;
}
double average(double a,double b)
{
double aver=2.0*a*b/(a+b);
return aver;
}
7.2
#include <iostream>
int input(double arr[],int n);
void show(double arr[],int n);
double average(double arr[],int n);
using namespace std;
const int Max=10;
int main()
{
double aver;
double arr[Max];
cout<<"Input "<<Max<<" scores: \n";
cout<<"# 1: ";
int n=input(arr,Max);
cout<<"The score: ";
show(arr,n);
aver=average(arr,n);
cout<<"The average is: "<<aver<<endl;
return 0;
}
int input(double arr[],int n)
{
int i=0;
while(cin>>arr[i]&&++i<n)
{
cout<<"# "<<i+1<<": ";
}
return i;
}
void show(double arr[],int n)
{
for(int i=0;i<n;i++)
{
cout<<arr[i]<<" ";
}
cout<<endl;
}
double average(double arr[],int n)
{
double sum=0.0;
for(int i=0;i<n;i++)
{
sum+=arr[i];
}
double aver=sum/n;
return aver;
}
7.3
#include <iostream>
using namespace std;
struct box
{
char maker[40];
float height;
float width;
float length;
float volume;
};
void volume(box * a);
void show(box a);
int main()
{
box A;
cout<<"The maker: ";
cin.get(A.maker,40).get();
cout<<"The height: ";
cin>>A.height;
cout<<"The width: ";
cin>>A.width;
cout<<"The length: ";
cin>>A.length;
volume(&A);
show(A);
return 0;
}
void show(box a)
{
cout<<"The maker: "<<a.maker<<endl;
cout<<"The height: "<<a.height<<endl;
cout<<"The width: "<<a.width<<endl;
cout<<"The lenght: "<<a.length<<endl;
cout<<"The volume: "<<a.volume<<endl;
}
void volume(box * a)
{
a->volume=a->height*a->width*a->length;
}
7.4
#include <iostream>
long double probability(unsigned numbers, unsigned picks, unsigned s);
int main()
{
using namespace std;
double total, choices, s;
cout << "Enter the total number of choices on the game card and\n"
"the number of picks allowed:\n";
while ((cin >> total >> choices>>s) && choices <= total)
{
cout << "You have one chance in ";
cout << probability(total, choices, s); // compute the odds
cout << " of winning.\n";
cout << "Next two numbers (q to quit): ";
}
cout << "bye\n";
// cin.get();
// cin.get();
return 0;
}
long double probability(unsigned numbers, unsigned picks, unsigned s)
{
long double result = 1.0; // here come some local variables
long double n;
unsigned p;
for (n = numbers, p = picks; p > 0; n--, p--)
result = result * n / p ;
result=result*s;
return result;
}
7.5
#include <iostream>
using namespace std;
long factorial(int n);
int main()
{
cout<<"Enter a number；";
int n;
long fac;
while(cin>>n&&n>=0)
{
fac=factorial(n);
cout<<"The factorial is: "<<fac<<endl;
cout<<"Enter another number: ";
}
cout<<"Bye.\n";
return 0;
}
long factorial(int n)
{
long fac;
if(n>0)
fac=n*factorial(n-1);
else
fac=1;
return fac;
}
7.6
#include <iostream>
using namespace std;
int Fill_arry(double num[],int n);
void Show_arry(double num[],int n);
void Reverse_arry(double num[],int n);
int main()
{
int n;
cout<<"How many numbers: ";
cin>>n;
double num[n];
cout<<"The 1 number: ";
n=Fill_arry(num,n);
cout<<"The numbers of the arry is: "<<n<<endl;
Show_arry(num,n);
Reverse_arry(num,n);
Show_arry(num,n);
Reverse_arry(num,n);
double tmp=num[0];
num[0]=num[n-1];
num[n-1]=tmp;
Show_arry(num,n);
return 0;
}
int Fill_arry(double num[],int n)
{
int i=0;
while(cin>>num[i] && ++i<n)
{
cout<<"The "<<i+1<<" number: ";
}
return i;
}
void Show_arry(double num[],int n)
{
cout<<"The arry is: ";
for(int i=0;i<n;i++)
{
cout<<num[i]<<" ";
}
cout<<endl;
}
void Reverse_arry(double num[],int n)
{
for(int i=0;i<n/2;i++)
{
double tmp=num[i];
num[i]=num[n-1-i];
num[n-1-i]=tmp;
}
}
7.7
#include <iostream>
const int Max = 5;
double *fill_array(double * ar_begin, double * ar_end);
void show_array(double * ar_begin, double * ar_end);
void revalue(double r, double * ar_begin, double * ar_end);
int main()
{
using namespace std;
double properties[Max];
double *p;
p = fill_array(properties, properties+Max);
show_array(properties, p);
if (properties!=p)
{
cout << "Enter revaluation factor: ";
double factor;
while (!(cin >> factor)) // bad input
{
cin.clear();
while (cin.get() != '\n')
continue;
cout << "Bad input; Please enter a number: ";
}
revalue(factor, properties, p);
show_array(properties, p);
}
cout << "Done.\n";
// cin.get();
// cin.get();
return 0;
}
double *fill_array(double * ar_begin, double * ar_end)
{
using namespace std;
double *p;
int i=1;
for (p=ar_begin; p!=ar_end; p++,i++)
{
cout << "Enter value #" << i << ": ";
cin >> *p;
if (!cin) // bad input
{
cin.clear();
while (cin.get() != '\n')
continue;
cout << "Bad input; input process terminated.\n";
break;
}
else if (*p < 0) // signal to terminate
break;
}
return p;
}
void show_array(double * ar_begin, double * ar_end)
{
using namespace std;
int i=1;
double *p;
for (p=ar_begin; p!=ar_end; p++,i++)
{
cout << "Property #" << i << ": $";
cout << *p << endl;
}
}
void revalue(double r, double * ar_begin, double * ar_end)
{
double *p;
for (p=ar_begin; p!=ar_end; p++)
*p *= r;
}
7.8(a)
//arrobj.cpp -- functions with array objects
#include <iostream>
using namespace std;
const int Seasons = 4;
const char * Snames[Seasons] =
{"Spring", "Summer", "Fall", "Winter"};
void fill(double * pa);
void show(double * da);
int main()
{
double expenses[Seasons];
fill(&expenses[Seasons]);
show(&expenses[Seasons]);
// std::cin.get();
// std::cin.get();
return 0;
}
void fill(double * pa)
{
for (int i = 0; i < Seasons; i++)
{
cout << "Enter " << Snames[i] << " expenses: ";
cin >> pa[i];
}
}
void show(double * da)
{
double total = 0.0;
cout << "\nEXPENSES\n";
for (int i = 0; i < Seasons; i++)
{
cout << Snames[i] << ": $" << da[i] << '\n';
total += da[i];
}
cout << "Total: $" << total << '\n';
}
7.8(b)
//arrobj.cpp -- functions with array objects
#include <iostream>
using namespace std;
const int Seasons = 4;
const char * Snames[Seasons] =
{"Spring", "Summer", "Fall", "Winter"};
struct cost
{
double expenses[Seasons];
};
void fill(cost *pa);
void show(cost da);
int main()
{
cost money;
fill(&money);
show(money);
// std::cin.get();
// std::cin.get();
return 0;
}
void fill(cost *pa)
{
for (int i = 0; i < Seasons; i++)
{
cout << "Enter " << Snames[i] << " expenses: ";
cin >> (*pa).expenses[i];
}
}
void show(cost da)
{
double total = 0.0;
cout << "\nEXPENSES\n";
for (int i = 0; i < Seasons; i++)
{
cout << Snames[i] << ": $" << da.expenses[i] << '\n';
total += da.expenses[i];
}
cout << "Total: $" << total << '\n';
}
7.9 （注释部分循环终止条件有误，却不知为何会出现这样的结果，如果有知道的大佬，还望不吝赐教）
#include <iostream>
#include <cstring>
using namespace std;
const int SLEN=30;
struct student
{
char fullname[SLEN];
char hobby[SLEN];
int ooplevel;
};
int getinfo(student pa[],int n);
void display1(student st);
void display2(const student * ps);
void display3(const student pa[],int n);
int main()
{
cout<<"Enter class size；";
int class_size;
cin>>class_size;
while(cin.get()!='\n')
continue;
student * ptr_stu=new student[class_size];
int entered=getinfo(ptr_stu,class_size);
for(int i=0;i<entered;i++)
{
display1(ptr_stu[i]);
display2(&ptr_stu[i]);
}
display3(ptr_stu,entered);
delete [] ptr_stu;
cout<<"Done\n";
return 0;
}
int getinfo(student pa[],int n)
{
// int i=0;
// cout<<"Enter the data about students: \n";
// cout<<"student 1: \n"<<"fullname: ";
// while(cin.get(pa[i].fullname,SLEN)!="\n")
// {
// cin.get();
// cout<<"hobby: ";
// cin.getline(pa[i].hobby,SLEN);
// cout<<"ooplevel:";
// cin>>pa[i].ooplevel;
// cin.get();
// i++;
// if(i==n)
// break;
// cout<<"student "<<i+1<<":\n"<<"fullname: ";
// }
int count=0;
for(int i=0;i<n;i++)
{
cout<<"student "<<i+1<<":\n"<<"fullname: ";
cin.getline(pa[i].fullname,SLEN);
if(strlen(pa[i].fullname)==0)
break;
cout<<"hobby: ";
cin.getline(pa[i].hobby,SLEN);
cout<<"ooplevel:";
cin>>pa[i].ooplevel;
cin.get();
count++;
}
cout<<endl;
return count;
}
void display1(student st)
{
cout << "The fullname: " << st.fullname << endl;
cout << "The hobby: " << st.hobby << endl;
cout << "The ooplevel: " << st.ooplevel << endl;
cout << endl;
}
void display2(const student * ps)
{
cout << "The fullname: " << ps->fullname << endl;
cout << "The hobby: " << ps->hobby << endl;
cout << "The ooplevel: " << ps->ooplevel << endl;
cout << endl;
}
void display3(const student pa[],int n)
{
for(int i=0;i<n;i++)
{
cout<<"The student "<<i+1<<":\n";
cout << "The fullname: " << pa[i].fullname << endl;
cout << "The hobby: " << pa[i].hobby << endl;
cout << "The ooplevel: " << pa[i].ooplevel << endl;
}
}
7.10
#include <iostream>
#include <string>
using namespace std;
double add (double x, double y);
double subtract (double x, double y);
double multiply (double x, double y);
double divide (double x, double y);
double calculate (double x, double y, double (*p)(double x, double y));
int main()
{
double x,y;
double (*pf[4])(double,double)={add,subtract,multiply,divide};
string name[4]={"add","subtrcat","multiply","divide"};
cout<<"Enter two numbers: ";
while(cin>>x>>y)
{
for(int i=0;i<4;i++)
{
cout<<name[i]<<": "<<calculate(x,y,pf[i])<<endl;
}
cout<<"Enter another two numbers: ";
}
cout<<"Done.\n";
return 0;
}
double add (double x, double y)
{
return x+y;
}
double subtract (double x, double y)
{
return x-y;
}
double multiply (double x, double y)
{
return x*y;
}
double divide (double x, double y)
{
return x/y;
}
double calculate (double x, double y, double (*p)(double x, double y))
{
return (*p)(x,y);
}