C++ premier plus 第六版 编程练习解答（第四章）

1.编写一个C++程序，如下述输出示例所示的那样请求并显示信息
备注：本题其实没必要使用结构体，重点在于使用cin.getline()函数。若直接使用cin()，则若first name输入中包含空格，空格后部分会被存入lastname变量。

#include <iostream>

struct message
{
	char firstname[20];
	char lastname[20];
	char grade;
	int age;
};

int main()
{
	using namespace std;
	message a;
	cout << "What is your first name? ";
	cin.getline(a.firstname,20);
	cout << "What is your last name? ";
	cin.getline(a.lastname,20);
	cout << "What letter grade do you deserve? ";
	cin >> a.grade;
	cout << "What is your age? ";
	cin >> a.age;
	cout << "Name: " << a.lastname << ", " << a.firstname << endl
		 << "Grade: " << a.grade << endl
		 << "Age: " << a.age << endl;
	return 0;
}

2.修改程序清单4.4，使用C++ string类而不是char数组。

#include <iostream>
#include <string>
int main()
{
	using namespace std;
	string name,dessert;

	cout << "Enter your name:\n";
	getline(cin,name);
	cout << "Enter your favourite dessert:\n";
	getline(cin,dessert);
	cout << "I have some delicious " << dessert;
	cout << " for you, " << name << endl;
	return 0;
}

3.编写一个程序，它要求用户首先输入其名，再输入其姓；然后程序使用一个逗号和空格将姓和名组合起来，并存储和显示组合结果。请使用char数组和头文件cstring中的函数。

#include <iostream>
#include <cstring>
int main()
{
	using namespace std;
	char first[20],last[20],full[20];
	cout << "Enter your first name: ";
	cin.getline(first,20);
	cout << "Enter your last name: ";
	cin.getline(last,20);
	strcpy(full,last);
	strcat(full,", ");
	strcat(full,first);
	cout << "Here is the information in a single string: " << full << endl;
	return 0;
}

4.编写一个程序，它要求用户首先输入其名，再输入其姓；然后程序使用一个逗号和空格将姓和名组合起来，并存储和显示组合效果。请使用string对象和头文件string中的函数。

#include <iostream>
#include <string>
int main()
{
	using namespace std;
	string first,last,full;
	cout << "Enter your first name: ";
	getline(cin,first);
	cout << "Enter your last name: ";
	getline(cin,last);
	full = last + ", " + first;
	cout << "Here is the information in a single string: " << full << endl;
	return 0;
}

5.结构CandyBar包含3个成员。第一个成员存储了糖块的品牌；第二个成员存储了糖块的重量（可以有小数）；第三个成员存储了糖块的卡路里含量（整数）。请编写一个程序，声明这个结构体，创建一个名为snack的CandyBar变量并初始化后输出。

#include <iostream>

struct CandyBar
{
	char brand[20];
	float weight;
	int num;
};

int main()
{
	using namespace std;
	CandyBar snack =
	{
		"Mocha Munch",
		2.3,
		350
	};
	cout << snack.brand << endl
		 << snack.weight << endl
		 << snack.num << endl;
	return 0;
}

6.结构CandyBar包含3个成员，如习题5所示。请编写一个程序，创建一个包含3个元素的CandyBar数组，并将它们初始化为所选择的值，然后显示每个结构的内容。

#include <iostream>

struct CandyBar
{
	char brand[20];
	float weight;
	int num;
};

int main()
{
	using namespace std;
	CandyBar snack[3] =
	{
		{"Mocha Munch",2.3,350},
		{"Cake",10.1,500},
		{"chocolate",6.8,60}
	};
	for (int i=0;i<3;i++)
	{
		cout << snack[i].brand << endl
			 << snack[i].weight << endl
		 	 << snack[i].num << endl;
	}
	return 0;
}

7.披萨饼分析服务

#include <iostream>

struct pizza
{
	char name[20];
	float size;
	float weight;
};

int main()
{
	using namespace std;
	pizza a;
	cout << "Please enter the name of your pizza: ";
	cin.getline(a.name,20);
	cout << "Please enter the size of your pizza: ";
	cin >> a.size;
	cout << "Please enter the weight of your pizza: ";
	cin >> a.weight;
	cout << a.name << endl
		 << a.size << endl
		 << a.weight << endl;
	return 0;
}

8.完成练习7，但使用new来为结构分配内存，而不是声明一个结构变量。

#include <iostream>

struct pizza
{
	char name[20];
	float size;
	float weight;
};

int main()
{
	using namespace std;
	pizza * a = new pizza;
	cout << "Please enter the size of your pizza: ";
	cin >> (* a).size;
	cout << "Please enter the name of your pizza: ";
	cin.get();
	cin.get(a->name,20);
	cout << "Please enter the weight of your pizza: ";
	cin >> (* a).weight;
	cout << (* a).name << endl
		 << (* a).size << endl
		 << (* a).weight << endl;
	return 0;
}

9.完成练习6，但使用new来动态分配数组，而不是声明一个包含3个元素的CandyBar数组。

#include <iostream>
#include <string>

using namespace std;

struct CandyBar
{
	string brand;
	double weight;
	int num;
};

int main()
{

	CandyBar * snack = new CandyBar[3];
	snack[0].brand = "Mocha Munch";
	snack[0].weight = 2.3;
	snack[0].num = 350;
	snack[0].brand = "Cake";
	snack[0].weight = 10.1;
	snack[0].num = 500;
	snack[0].brand = "chocolate";
	snack[0].weight = 6.8;
	snack[0].num = 60;
	for (int i=0;i<3;i++)
	{
		cout << snack[i].brand << endl
			 << snack[i].weight << endl
		 	 << snack[i].num << endl;
	}
	return 0;
}

10.编写一个程序，让用户输入3次40码跑成绩并显示次数和平均成绩。

#include <iostream>
#include <array>

int main()
{
	using namespace std;
	array<double,3> grade;
	double sum,average;
	sum = 0;
	cout << "Please enter the grades: " << endl;

	for (int i = 0; i < 3; i ++)
	{
		cout << "The " << i+1 << " time: ";
		cin >> grade[i];
		sum = sum +grade[i];
	}

	average = sum / 3;
	cout << "The average grade for 3 time is: " << average << endl;
	return 0;
}