C++ prime Plus 第四章编程练习答案

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总结

数组，例如：int card[4] = {3, 6, 8, 10};
字符串，例如：string str = “Hello world!”;
C风格字符串是一个特殊的字符数组，以空字符（’\0’）表示字符串的结束。
结构体定义
指针，例如：
int months =12;
int* p = &months;
int* pt = new int[12];
解决cin忽略空格和换行符的问题用getline()和get()，例如
char FirstName[20];
string LastName;
cin.getline(FirstName, 20);
getline(cin, LastName);
cin.get(FirstName, 20);
cin.get();

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一、第一题

题目：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：
What is your first name? Beety Sue
What is your last name? Yewe
What letter grade do you deserve? B
What is your age? 22
Name: Yewe, Betty Sue
Grade: C
Age: 22
注意，该程序应该接受的名字包含多个单词。另外，程序将向下调整成绩，即向上调一个字母。假设用户请求A、B或C，所以不必担心D和F之间的空档。

#include 
int main() {
    using std::cout;
    using std::cin;
    const int ArSize = 15;
    char FirstName[ArSize];
    char LastName[ArSize];
    char Grade;
    int Age;

    cout << "what is your first name? ";
    cin.getline(FirstName, 15);
    cout << "what is your last name? ";
    cin.getline(LastName, 15);

    cout << "what letter grade do you deserve? ";
    cin >> Grade;
    cout << "what is your age? ";
    cin >> Age;
    std::cout << "name: " << LastName << ", " << FirstName << std::endl;
    cout << "Grade: " << char(Grade + 1) << std::endl;
    cout << "Age: " << Age << std::endl;

    return 0;
}

二、第二题

题目：修改程序清单4.4，使用C++ string类而不是char数组。

#include 
#include 
int main() {
	using namespace std;
	std::string name;
	std::string dessert;

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

三、第三题

题目：编写一个程序，它要求用户首先输入其名，然后输入其姓；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。下面是该程序运行时的情形：
Enter your first name: Flip
Enter your last name: Fleming
Here’s the information in a single string: Fleming , Flip

#include 
#include 
int main() {
    using std::cout;
    using std::cin;
    const int ArSize = 30;
    char FirstName[ArSize];
    char LastName[ArSize];
    char TotalName[ArSize*2];
    cout << "Enter your first name: ";
    cin.getline(FirstName, ArSize);
    cout << "Enter your last name: ";
    cin.getline(LastName, ArSize);
    strcpy_s(TotalName, LastName);
    strcat_s(TotalName, ", ");
    strcat_s(TotalName, FirstName);
    cout << "Here's the information: " << TotalName;
    return 0;
}

四、第四题

题目：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string对象和头文件string中的函数。下面是该程序运行时的情形：
Enter your first name: Flip
Enter your last name: Fleming
Here’s the information in a single string: Fleming, Flip

#include 
#include 
int main() {
    using std::cout;
    using std::cin;
    using std::string;
    string FirstName;
    string LastName;
    string TotalName;
    cout << "Enter your first name: ";
    getline(cin, FirstName);
    cout << "Enter your last name: ";
    getline(cin, LastName);
    TotalName = LastName + ", " + FirstName;
    cout << "Here's the information: " << TotalName;
    return 0;
}

五、第五题

题目：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，创建一个名为snack的CandyBar变量，并将其成员分别初始化为“Mocha Munch”、2.3和350。初始化应在声明snack时进行。最后，程序显示snack变量的内容。

#include 
struct CandyBar
{
    std::string Brand;
    float Weight;
    int Calorie;
};
int main() {
    CandyBar snack = {"Mocha Munch", 2.3, 350};
    std::cout << snack.Brand << std::endl;
    std::cout << snack.Weight << std::endl;
    std::cout << snack.Calorie << std::endl;
    return 0;
}

六、第六题

题目：结构CandyBar包含3个成员，如编程练习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 
struct CandyBar
{
    std::string Brand;
    float Weight;
    int Calorie;
};
int main() {
    CandyBar snack[3] = {
        {"Aocha Aunch", 2.3, 350},
        {"Bocha Bunch", 4.56, 123},
        {"Cocha Cunch", 7.8910, 6778}
    };
    std::cout << snack[0].Brand << " " << snack[0].Weight << " " << snack[0].Calorie << std::endl;
    std::cout << snack[1].Brand << " " << snack[1].Weight << " " << snack[1].Calorie << std::endl;
    std::cout << snack[2].Brand << " " << snack[2].Weight << " " << snack[2].Calorie << std::endl;
    return 0;
}

七、第七题

题目：William Wingate从事比萨饼分析服务。对于每个披萨饼，他都需要记录下列信息：
（1）披萨饼公司的名称，可以有多个单词组成
（2）披萨饼的直径
（3）披萨饼的质量
请设计一个能够存储这些信息的结构，并编写一个使用这种结构变量的程序。程序将请求用户输入上述信息，然后显示这些信息。请使用cin和cout。

#include 
#include 
struct pizza
{
    char company[40];
    float height;
    float weight;
};
int main() {
    using std::cout;
    using std::cin;
    pizza pizza;
    cout << "please input company: ";
    cin.getline(pizza.company, 40);
    cout << "please input height: ";
    cin >> pizza.height;
    cout << "please input weight: ";
    cin >> pizza.weight;
    cout << pizza.company << " " << pizza.height << " " << pizza.weight;
    return 0;
}

八、第八题

题目：完成编程练习7，但使用new来为结构分配内存，而不是声明一个结构变量。另外，让程序在请求输入比萨饼公司名称之前输入比萨饼的直径。

#include 
#include 
struct Pizza
{
    char company[40];
    float height;
    float weight;
};
int main() {
    using std::cout;
    using std::cin;
    Pizza* pizza = new Pizza;
    cout << "please input company: ";
    cin.getline(pizza->company, 40);
    cout << "please input height: ";
    cin >> pizza->height;
    cout << "please input weight: ";
    cin >> pizza->weight;
    cout << pizza->company << " " << pizza->height << " " << pizza->weight;
    return 0;
}

九、第九题

题目：完成编程练习6，但是用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 
#include 
struct Pizza
{
    std::string company;
    double height;
    double weight;
};
int main() {
    using std::cout;
    using std::cin;
    Pizza* pizza = new Pizza[3];
    for (int i = 0; i < 3; i++) {
        cout << "please input company: ";
        getline(cin, pizza[i].company);
        cout << "please input height: ";
        cin >> pizza[i].height;
        cout << "please input weight: ";
        cin >> pizza[i].weight;
        cin.get();
    }
    for (int i = 0; i < 3; i++) {
        cout << (pizza + i)->company << " " << (pizza + i)->height << " " << (pizza + i)->weight << std::endl;
        cout << pizza[i].company << " " << pizza[i].height << " " << pizza[i].weight << std::endl;
        cout << std::endl;
    }
    return 0;
}

十、第十题

题目：编写一个程序，让用户输入三次40码跑的成绩（如果您愿意，也可让用户输入40米跑的成绩）。并显示次数和平均成绩。请使用一个array对象来存储数据（如果编译器不支持array类，请使用数组）。

#include 
#include 
int main() {
	using std::cin;
	std::array<float, 3>runtime;
	float average;
	cin >> runtime[0]>>runtime[1]>>runtime[2];
	std::cout << runtime[0] << std::endl;
	std::cout << runtime[1] << std::endl;
	std::cout << runtime[2] << std::endl;
	average = (runtime[0] + runtime[1] + runtime[2]) / 3;
	std::cout << average;
	return 0;
}

谢谢观看，祝顺利。