C++ Primer Pluse 课后习题答案 第四章

#include<iostream>
#include<string>
#include<cstring>
#include<array>

using namespace std;
// practice 1
void p4_1(void)
{
    string firstname;
    string lastname;
    char grade;
    int age;
    cout << "What is your first name? ";
    getline(cin,firstname);
    cout  << "What is your last name? ";
    getline(cin, lastname);
    cout  << "What letter grade do you deserve? ";
    cin >> grade;
    cout  << "What is your age? ";
    cin >> age;
    cin.get();
    cout << "Name: " << lastname << ", " << firstname << endl;
    grade = int(grade + 1);
    cout << "Grade: " << char(grade) << endl;
    cout << "Age: " << age << endl;
}

// practice 2
void p4_2(void)
{
    const int ArSize = 20; // 这句可以去掉
    string name;
    string 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 << ".\n";

    return;
}
// practice 3
void p4_3()
{
    char firstname[40];
    char lastname[40];
    char name[80] = { ‘\0‘ };
    cout << "Enter your first name: ";
    cin.getline(firstname, 40);
    cout << "Enter your last name ";
    cin.getline(lastname, 40);
    strcpy_s(name, 80,lastname);
    strcat_s(name, 80 ,", ");
    strcat_s(name, 80, firstname);
    cout << "Here‘s the information in a single string: " << name << endl;
}

// practice 4
void p4_4(void)
{
    string firstname;
    string lastname;
    string name;
    string band = ", ";
    cout << "Enter your first name: ";
    getline(cin, firstname);
    cout << "Enter your last name ";
    getline(cin, lastname);
    name = lastname + band + firstname;
    cout << "Here‘s the information in a single string: " << name << endl;
}
// practice 5
struct CandyBar
{
    char brand[40];
    float weight;
    int calorie;
};
void p4_5(void)
{
    CandyBar snack = { "Mocha Munch", 2.3, 350};
    cout << "snack.brand = " << snack.brand << endl;
    cout << "snack.weight = " << snack.weight << endl;
    cout << "snack.calorie = " << snack.calorie << endl;
}
//practice 6
void p4_6(void)
{
    CandyBar snack[3];
    snack[0] = { "a",0.1,1 };
    snack[1] = { "b",0.2,2 };
    snack[2] = { "c",0.3,3 };
    cout << "snack[0].brand = " << snack[0].brand << endl;
    cout << "snack[1].weight = " << snack[1].weight << endl;
    cout << "snack[2].calorie = " << snack[2].calorie << endl;
}
//practice 7
struct Pizza
{
    char company[40];
    double diameter;
    double weight;
};
void p4_7(void)
{
    Pizza example;
    cout << "Enter the pizza company name: " << endl;
    cin.getline(example.company, 40);
    cout << "Enter the pizza diameter in inch: " << endl;
    cin >> example.diameter;
    cout << "Enter the pizza weight in pound: " << endl;
    cin >> example.weight;

    cout << "example.company = " << example.company << endl;
    cout << "example.diameter = " << example.diameter << " inches" << endl;
    cout << "example.weight = " << example.weight << " pounds" << endl;
}
//practice 8
void p4_8(void)
{
    Pizza* pt = new Pizza;
    cout << "Enter the pizza diameter in inch: " << endl;
    cin >> pt->diameter;
    cin.get();
    cout << "Enter the pizza company name: " << endl;
    cin.getline(pt->company, 40);
    cout << "Enter the pizza weight in pound: " << endl;
    cin >> pt->weight;

    cout << "diameter = " << pt->diameter << endl;
    cout << "company = " << pt->diameter << " inches" << endl;
    cout << "weight = " << pt->weight << " pounds" << endl;
    delete pt;
}
//practice 9
void p4_9(void)
{
    CandyBar* snack = new CandyBar[3];
    snack[0] = { "a",0.1,1 };
    snack[1] = { "b",0.2,2 };
    snack[2] = { "c",0.3,3 };
    cout << "snack[0].brand = " << (*snack).brand << endl;
    cout << "snack[1].weight = " << (*(snack+1)).weight << endl;
    cout << "snack[2].calorie = " << snack[2].calorie << endl;

    delete [] snack;
}
//practice 10
void p4_10()
{
    double ave_grade;
    array<double, 3>grade;
    cout << "Enter your grades of 40-meters-match in seconds: " << endl;
    cin >> grade[0] >> grade[1] >> grade[2];
    ave_grade = (grade[0] + grade[1] + grade[2]) / 3.0;
    cout << "第一次: " << grade[0] << " s" << endl;
    cout << "第二次: " << grade[1] << " s" << endl;
    cout << "第三次: " << grade[2] << " s" << endl;
    cout << "平均成绩: " << ave_grade << " s" << endl;
}

int main()
{
    p4_10();
    return 0;
}