C++ primer plus 第六版 第四章 编程练习答案

第四章 编程练习答案

1.

#include<iostream>

int main()
{
    using namespace std;

    cout << "What is your first name? ";
    char firstname[20];
    cin.getline(firstname, 20);//输入字符串
    cout << "What is your last name? ";
    char lastname[20];
    cin.getline(lastname, 20);
    cout << "What letter grade do you deserve? ";
    char grade;
    cin >> grade;
    grade = grade + 1;
    cout << "What is your age? ";
    int age;
    cin >> age; 

    cout << "Name: " << lastname << ", " << firstname << endl;  
    cout << "Grade: " << grade << endl;
    cout << "Age: " << age << endl;
    return 0;           
}

2.

#include<iostream>
#include<string>//string类的函数库

int main()
{
    using namespace std;

    string name;
    string dessert;

    cout << "Enter your name:\n";
    getline(cin, name);//输入string类
    cout << "Enter your favorite dessert:\n";
    getline(cin, dessert);
    cout << "I have some delicious " << dessert;
    cout << " for you, " << name << ".\n";
    return 0;

}

3.

#include<iostream>
#include<cstring>

int main()
{
    using namespace std;

    char firstname[20];
    string lastname;

    cout << "Enter your first name: ";
    cin.getline(firstname, 20);//输入字符串
    cout << "Enter your last name: ";
    getline(cin, lastname);//输入string类
    cout << "Here's the information in a single string: " 
         << lastname << ", " << firstname << endl;  

    return 0;

}

4.

题目3和4的区别在于char数组和string的区别，其他一致，就不放了。

5.

#include<iostream>
struct CandyBar{
    char brand[20];
    float weight;
    int calories;
};

int main()
{
    using namespace std;
    CandyBar snack = {"Mocha Munch", 2.3, 350};

    cout << "Brand: " << snack.brand << endl;
    cout << "Weight: " << snack.weight << endl;
    cout << "calories: " << snack.calories << endl;
    return 0;
}

6.

#include<iostream>
struct CandyBar{
    char brand[20];
    float weight;
    int calories;
};

int main()
{
    using namespace std;
    CandyBar snack[3] = {
        {"Mocha Munch1", 2.3, 350},
        {"Mocha Munch2", 1.1, 150},
        {"Mocha Munch3", 1.3, 450}, 

    };

    for(int i=0;i<3;i++)
    {
        cout << "Brand: " << snack[i].brand << endl;//这里直接用成员运算符(.)
        cout << "Weight: " << snack[i].weight << endl;
        cout << "calories: " << snack[i].calories << endl;
    }
    return 0;
}

7.

#include<iostream>
struct pizza{

    char brand[20];
    float length;
    float weight;

};

int main()
{
    using namespace std;
    int n;
    cout << "Please enter the number of the pizza: "; 
    cin >> n;
    cin.get();//注意这里数字末尾的换行符 
    pizza AAA[n];

    for(int i = 0;i < n ; i++)
    {   
        cout << "Brand: " << endl;
        cin.getline(AAA[i].brand, 20);
        cout << "Weight: " << endl;
        cin >> AAA[i].weight;
        cout << "length: " << endl;
        cin >> AAA[i].length;
        cin.get();
    }   

    cout << "\nHere is the information of the pizza: " << endl; 
    for(int i = 0;i < n ; i++)
    {
        cout << "pizza #" << i+1 << ": " << endl;
        cout << "length: " << AAA[i].length << endl;
        cout << "Brand: " << AAA[i].brand << endl;
        cout << "Weight: " << AAA[i].weight << endl;
    }   

    return 0;
}

8.

#include<iostream>
struct pizza{   
    char brand[20];
    float length;
    float weight;   
};

int main()
{
    using namespace std;
    int n;
    cout << "Please enter the number of the pizza: "; 
    cin >> n;
    pizza * AAA = new pizza[n];//动态分配内存 

    for(int i = 0;i < n ; i++)
    {
        cout << "pizza #" << i+1 << ": " << endl;
        cout << "length: " << endl;
        cin >> AAA[i].length;
        cin.get();//注意这里数字末尾的换行符 
        cout << "Brand: " << endl;
        cin.getline(AAA[i].brand, 20);
        cout << "Weight: " << endl;
        cin >> AAA[i].weight;
    }

    cout << "Here is the information of the pizza: " << endl; 
    for(int i = 0;i < n ; i++)
    {
        cout << "pizza #" << i+1 << ": " << endl;
        cout << "length: " << AAA[i].length << endl;
        cout << "Brand: " << AAA[i].brand << endl;
        cout << "Weight: " << AAA[i].weight << endl;
    }
    return 0;
}

9.

#include<iostream>
#include<string>
using namespace std;

struct CandyBar{
    string brand;
    float weight;
    int calories;
};

int main()
{
    CandyBar * snack = new CandyBar[3];//动态分配数组

    snack[0] = {"Mocha Munch1", 2.3, 350};
    snack[1] = {"Mocha Munch2", 1.1, 150};
    snack[2] = {"Mocha Munch3", 1.3, 450};  

    for(int i=0;i<3;i++)
    {
    cout << "Brand: " << snack[i].brand << endl;
    cout << "Weight: " << snack[i].weight << endl;
    cout << "calories: " << snack[i].calories << endl;
    }
    return 0;
}

10.

#include<iostream>

int main()
{
    using namespace std;
    double runtime[3], average;
    int i;
    for(i=0;i<3;i++){
        cout << "输入第" << i+1 << "次时间：" << endl;
        cin >> runtime[i];
    }

    average = (runtime[0] + runtime[1] + runtime[2]) / 3;
    cout << "平均时间:" << average << endl;

    return 0;

}