2018-11-06 623 views 1

C++ Primer Plus（第五版）第7章编程题答案

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=2.0*x*y/(x+y)

//C++ Primer Plus Edition 5
//Chapter 7 Homework 1
#include<iostream>
using namespace std;
double heaver(int m, int n);
int main() {
	double m, n, ans;
	cout << "Please input two numbers: ";
	cin >> m >> n;
	while (m != 0 && n != 0) {
		ans = heaver(m, n);
		cout << "The answer is " << ans << endl;
		cout << "Please input two numbers: ";
		cin >> m >> n;
	}

	cout << "Done!" << endl;
	system("pause");
	return 0;
}

double heaver(int m, int n) {
	double res;
	res = 2.0*m*n / (m + n);
	return res;
}

//C++ Primer Plus Edition 5

//Chapter 7 Homework 1

#include<iostream>

using namespace std;

double heaver(int m, int n);

int main() {

double m, n, ans;

cout << "Please input two numbers: ";

cin >> m >> n;

while (m != 0 && n != 0) {

ans = heaver(m, n);

cout << "The answer is " << ans << endl;

cout << "Please input two numbers: ";

cin >> m >> n;

}

cout << "Done!" << endl;

system("pause");

return 0;

}

double heaver(int m, int n) {

double res;

res = 2.0*m*n / (m + n);

return res;

}

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。

//C++ Primer Plus Edition 5
//Chapter 7 Homework 2
#include<iostream>
using namespace std;
const int MAXSIZE = 10;
int fill_array(double scores[], int limit);
void show_array(const double ar[], int n);
double aver_array(double arc[], int n);
int main() {
	double scores[MAXSIZE];
	double average;
	cout << "Please enter ten scores:" << endl;
	int size = fill_array(scores, MAXSIZE);
	cout << "The scores are:" << endl;
	show_array(scores, size);
	average = aver_array(scores, size);
	cout << "The average score is " << aver_array(scores, size) << endl;
	system("pause");
	return 0;
}
int fill_array(double scores[], int limit) {
	double temp;
	int i;
	for (i = 0; i < limit; i++) {
		cout << "Enter Score #" << i << ": ";
		cin >> temp;
		if (!cin) {
			cin.clear();
			while (cin.get() != '\n')
				continue;
			break;
		}
		else if (temp < 0)
			break;
		scores[i] = temp;
	}
	return i;


}
void show_array(const double ar[], int n) {
	for (int i = 0; i < n; i++) {
		cout << "Score #" << (i + 1) << ": " << ar[i] << endl;
	}
}
double aver_array(double arc[], int n) {
	double total = 0;
	double average;
	for (int i = 0; i < n; i++) {
		total += arc[i];
	}
	average = total / n;
	return average;

}

//C++ Primer Plus Edition 5

//Chapter 7 Homework 2

#include<iostream>

using namespace std;

const int MAXSIZE = 10;

int fill_array(double scores[], int limit);

void show_array(const double ar[], int n);

double aver_array(double arc[], int n);

int main() {

double scores[MAXSIZE];

double average;

cout << "Please enter ten scores:" << endl;

int size = fill_array(scores, MAXSIZE);

cout << "The scores are:" << endl;

show_array(scores, size);

average = aver_array(scores, size);

cout << "The average score is " << aver_array(scores, size) << endl;

system("pause");

return 0;

}

int fill_array(double scores[], int limit) {

double temp;

int i;

for (i = 0; i < limit; i++) {

cout << "Enter Score #" << i << ": ";

cin >> temp;

if (!cin) {

cin.clear();

while (cin.get() != '\n')

continue;

break;

}

else if (temp < 0)

break;

scores[i] = temp;

}

return i;

}

void show_array(const double ar[], int n) {

for (int i = 0; i < n; i++) {

cout << "Score #" << (i + 1) << ": " << ar[i] << endl;

}

double aver_array(double arc[], int n) {

double total = 0;

double average;

for (int i = 0; i < n; i++) {

total += arc[i];

}

average = total / n;

return average;

}

3.下面是一个结构声明：
//省略
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。

//C++ Primer Plus Edition 5
//Chapter 7 Homework 3
#include<iostream>
using namespace std;
struct box {
	char maker[40];
	float height;
	float width;
	float length;
	float volume;
};
void show_box(box member);
void set_box(box *pmember);
int main() {
	box b = { "Yu Shuai",3,2,1,1 };
	show_box(b);
	set_box(&b);
	show_box(b);
	system("pause");
	return 0;
}
void show_box(box member) {
	cout << "Box's Maker: " << member.maker << endl;
	cout << "Box's height: " << member.height << endl;
	cout << "Box's width: " << member.width << endl;
	cout << "Box's length: " << member.length << endl;
	cout << "Box's volume: " << member.volume << endl;
}

void set_box(box *pmember) {
	(*pmember).volume = (*pmember).height*(*pmember).length*(*pmember).width;
}

//C++ Primer Plus Edition 5

//Chapter 7 Homework 3

#include<iostream>

using namespace std;

struct box {

char maker[40];

float height;

float width;

float length;

float volume;

};

void show_box(box member);

void set_box(box *pmember);

int main() {

box b = { "Yu Shuai",3,2,1,1 };

show_box(b);

set_box(&b);

show_box(b);

system("pause");

return 0;

}

void show_box(box member) {

cout << "Box's Maker: " << member.maker << endl;

cout << "Box's height: " << member.height << endl;

cout << "Box's width: " << member.width << endl;

cout << "Box's length: " << member.length << endl;

cout << "Box's volume: " << member.volume << endl;

}

void set_box(box *pmember) {

(*pmember).volume = (*pmember).height*(*pmember).length*(*pmember).width;

}

4. 许多州的彩票发行结构都使用如程序清单7.4所示的简单彩票玩法的变体。在这些玩法中，玩家从一组被称为域号码（field number）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几率与选中号码几率的乘积。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。请修改程序清单7.4，以计算中得这种彩票头奖的几率。

//C++ Primer Plus Edition 5
//Chapter 7 Homework 4
#include<iostream>
const int n1 = 5;
const int num1 = 47;
const int n2 = 1;
const int num2 = 27;
long double odds(unsigned num, unsigned n);
int main()
{
using namespace std;
double odds1 = odds(num1, n1);
double odds2 = odds(num2, n2);
cout << "中头奖的几率为: " << odds1*odds2 << endl;
system("pause");
return 0;
}
long double odds(unsigned num, unsigned n)
{
using namespace std;
long double res = 1.0;
for (num, n; n > 0; n--, num--)
res = res * n / num;
return res;
}

//C++ Primer Plus Edition 5

//Chapter 7 Homework 4

#include<iostream>

const int n1 = 5;

const int num1 = 47;

const int n2 = 1;

const int num2 = 27;

long double odds(unsigned num, unsigned n);

int main()

{

using namespace std;

double odds1 = odds(num1, n1);

double odds2 = odds(num2, n2);

cout << "中头奖的几率为: " << odds1*odds2 << endl;

system("pause");

return 0;

}

long double odds(unsigned num, unsigned n)

{

using namespace std;

long double res = 1.0;

for (num, n; n > 0; n--, num--)

res = res * n / num;

return res;

}

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。

//C++ Primer Plus Edition 5
//Chapter 7 Homework 5
#include<iostream>
using namespace std;
int factorial(int n);
int main() {
	int n, ans;
	cout << "Please input an integer: ";
	cin >> n;
	ans = factorial(n);
	cout << "The answer is " << ans << endl;
	system("pause");
	return 0;
}
int factorial(int n) {
	int res = 1;
	if (n > 1)
		res = n*factorial(n-1);
	return res;
}

//C++ Primer Plus Edition 5

//Chapter 7 Homework 5

#include<iostream>

using namespace std;

int factorial(int n);

int main() {

int n, ans;

cout << "Please input an integer: ";

cin >> n;

ans = factorial(n);

cout << "The answer is " << ans << endl;

system("pause");

return 0;

}

int factorial(int n) {

int res = 1;

if (n > 1)

res = n*factorial(n-1);

return res;

}

6.编写一个程序，它使用下列函数：

Fill_array()将一个double数组的名称和长度作为参数。它提示用户输入double值，并将这些值存储到数组中。当数组被填满或用户输入了非数字时，输入将停止，并返回实际输入了多少个数字。
Show_array()将一个double数组的名称和长度作为参数，并显示该数组的内容。
Reverse_array()将一个double数组的名称和长度作为参数，并将存储在数组中的值的顺序反转。
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。

//C++ Primer Plus Edition 5
//Chapter 7 Homework 6
#include<iostream>
int fill_array(double ar[], int limit);
void show_array(double ar[], int size);
void reverse_array(double ar[], int size);
using namespace std;
const int MAXSIZE = 20;
int main()
{
	int n;
	double shuzu[MAXSIZE];
	int size = fill_array(shuzu, MAXSIZE);
	show_array(shuzu, size);
	reverse_array(shuzu, size);
	cout << "反转结果：" << endl;
	show_array(shuzu, size);
	system("pause");
	return 0;
}
int fill_array(double ar[], int limit)
{
	double temp;
	int i;
	for (i = 0; i<limit; i++)
	{
		cout << "Enter value#" << (i + 1) << " \n";
		cin >> temp;
		if (!cin)
		{
			cin.clear();
			cout << "bad input:\n";
			break;
		}
		else
			ar[i] = temp;
	}
	return i;
}
void show_array(double ar[], int size)
{
	for (int i = 0; i<size; i++)
		cout << "Value #" << (i + 1) << ": " << ar[i] << endl;;
}
void reverse_array(double ar[], int size)
{
	int i, j;
	for (i = 1, j = size - i - 1; i<j; i++, j--)
	{
		double temp = ar[i];
		ar[i] = ar[j];
		ar[j] = temp;
	}
}

//C++ Primer Plus Edition 5

//Chapter 7 Homework 6

#include<iostream>

int fill_array(double ar[], int limit);

void show_array(double ar[], int size);

void reverse_array(double ar[], int size);

using namespace std;

const int MAXSIZE = 20;

int main()

{

int n;

double shuzu[MAXSIZE];

int size = fill_array(shuzu, MAXSIZE);

show_array(shuzu, size);

reverse_array(shuzu, size);

cout << "反转结果：" << endl;

show_array(shuzu, size);

system("pause");

return 0;

}

int fill_array(double ar[], int limit)

{

double temp;

int i;

for (i = 0; i<limit; i++)

{

cout << "Enter value#" << (i + 1) << " \n";

cin >> temp;

if (!cin)

{

cin.clear();

cout << "bad input:\n";

break;

}

else

ar[i] = temp;

}

return i;

}

void show_array(double ar[], int size)

{

for (int i = 0; i<size; i++)

cout << "Value #" << (i + 1) << ": " << ar[i] << endl;;

}

void reverse_array(double ar[], int size)

{

int i, j;

for (i = 1, j = size - i - 1; i<j; i++, j--)

{

double temp = ar[i];

ar[i] = ar[j];

ar[j] = temp;

}

7. 修改程序清单7.7中的3个数组处理函数，使之使用两个指针参数来表示区间。fill_array()函数不返回实际读取了多少个数字，而是返回一个指针，该指针指向最后被填充的位置；其他的函数可以将该指针作为第二个参数，以标识数据结尾。

//C++ Primer Plus Edition 5
//Chapter 7 Homework 7
#include<iostream>
using namespace std;
const int Max = 5;
double* fill_array(double *ar, double *limit);
void show_array(const double *ar, double *n);
void revalue(double r, double *ar, double *n);

int main() {
	double properties[Max];
	double *size = fill_array(properties, properties+Max);
	show_array(properties, size);
	cout << "Enter revaluation factor: ";
	double factor;
	cin >> factor;
	revalue(factor, properties, size);
	show_array(properties, size);
	cout << "Done.\n";
	system("pause");
	return 0;
}
double *fill_array(double *ar, double *limit) {
	double temp;
	double *p;
	for (p=ar; p < limit; p++) {
		cout << "Enter value: ";
		cin >> temp;
		if (!cin) {
			cin.clear();
			while (cin.get() != '\n')
				continue;
			cout << "Bad input;input process terminated.\n";
			break;
		}
		else if (temp < 0)
			break;
		*p = temp;
	}
	return p;
}

void show_array(const double *ar, double *n) {
	for (const double *p = ar; p < n; p++)
	{
		cout << "Property: $";
		cout << *p << endl;
	}
}

void revalue(double r, double *ar, double *n) {
	for (ar; ar < n; ar++)
		(*ar) *= r;
}