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)
#include <iostream>
double average(double a, double b);
int main(void)
{
using namespace std;
double a;
double b;
double avr;
cout << "Please enter two numbers: ";
cin >> a >> b;
while (a != 0 && b != 0)
{
avr = average(a, b);
cout << "The average is: " << avr << endl;
cout << "Please enter two numbers: ";
cin >> a >> b;
}
cout << "Done!" << endl;
return 0;
}
double average(double a, double b)
{
double avr;
avr = 2.0 * a * b / (a + b);
return avr;
}
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。
#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 avr = sum / n;
return avr;
}
3.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。
#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;
}
4.请修改程字请单7.4,以计算中得这种彩票头奖的几率。
#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";
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;
}
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
#include <iostream>
using namespace std;
long factorial(int n);
int main()
{
cout<<"Please enter a number；";
int n;
long f;
while(cin >> n && n >= 0)
{
f = factorial(n);
cout << "The factorial is: " << f << 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;
}
6.程序将使用这些函数来填充数组然后显示数组；反转数组然后显示数组；反转数组中除第一个和最后一个元素之外的所有元素，然后显示数组。
#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.修改程序清单7.7中的三个数组处理函数，使之使用两个指针参数来表示区间。
#include <iostream>
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[5];
double *p;
p = fill_array(properties, properties + 5);
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." << endl;
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)
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;
}
8.在不使用array类的情况下完成程序清单7.15所做的工作。编写两个这样的版本。
(a)使用const char *数组存储表示季度名称的字符串，并使用double输出存储开支。
#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]);
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';
}
(b)使用const char *数组存储表示季度名称的字符串，并使用一个结构，该结构只有一个成员，一个用于存储开支的double数组。
#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);
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';
}
9.这个练习让您编写处理数组和结构的函数。
#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 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;
}
}
#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);
}
