【學習筆記】C++ Primer Plus 課後編程習題——第四章

記錄一下自己看書做題的代碼，也記錄一下學習遇到的問題。代碼都是自己寫的，有錯誤請指出。

1.

// 4_13_1.cpp -- exercise 4.13.1
#include <iostream>
int main()
{
    using namespace std;
    cout << "What's your first name? ";
    char fstname[20];
    cin.getline(fstname, 20);
    cout << "What's your last name? ";
    string lstname;
    cin >> lstname;
    cout << "What letter grade do you deserve? ";
    char grade;
    cin >> grade;
    cout << "What's your age? ";
    int age;
    cin >> age;
    cout << "Name: " << lstname << "," << fstname << endl;
    cout << "Grade: " << char(grade + 1) << endl;
    cout << "Age: " << age << endl;

    return 0;
}

2.

//4_13_2.cpp --4.13.2 exercise
#include<iostream>
int main()
{
    using namespace std;
    string name;
    string desert;

    cout << "Enter your name:\n";
    getline(cin, name);
    cout << "Enter your favorite dessert:\n";
    getline(cin, desert);
    cout << "I have some delicious " << desert;
    cout << " for you, " << name << endl;

    return 0;
}

以上兩道題一個考點是ASCII碼與對應的字符串的轉換，還有就是cin.getline及getline函數的應用。

---

3.

// 4_13_3.cpp -- 4.13.3 exercise
#include<iostream>

int main()
{
    using namespace std;
    cout << "Enter your first name: ";
    char fstname[20];
    cin >> fstname;
    cout << "Enter your last name: ";
    char lstname[20];
    cin >> lstname;
    cout << "Here's the information in a single string: " << lstname << ", " << fstname;

    return 0;
}

這道題考了字符串的拼接。

---

4.

// 4_13_4.cpp -- exercise 4.13.4
#include <iostream>
#include <string>

int main()
{
    using namespace std;

    cout << "Enter your first name: ";
    string fstname;
    getline(cin, fstname);
    cout << "Enter your last name: ";
    string  lstname;
    getline(cin, lstname);
    cout << "Here's the information in a single string: " << lstname + ", " + fstname << endl;

    return 0;
}

考察了string類型的拼接，相比於char來說方便很多。

---

5.

// 4_13_5.cpp -- exercise 4.13.5
#include <iostream>

int main()
{
    using namespace std;

    struct CandyBar
    {
        string name;
        float weight;
        int Calorie;
    };

    CandyBar snacks =
    {
        "Mocha Munch",
        2.3,
        350
    };

    cout << "The name of this snack is " << snacks.name << "." << endl;
    cout << "The weight of it is " << snacks.weight << endl;
    cout << "The Calorie of it is " << snacks.Calorie << endl;

    return 0;
}

考察瞭如何創建struct。

---

6.

// 4_13_6.cpp -- exercise 4.13.6
#include <iostream>

int main()
{
    using namespace std;

    struct CandyBar
    {
        string name;
        float weights;
        int calorie;
    };

    CandyBar snacks[3] =
    {
        {"Barone", 2.0, 350},
        {"Bartwo", 2.1, 360},
        {"Barthree", 2.2, 370}
    };

    cout << "Names of snacks are:" << snacks[0].name << " " << snacks[1].name << " "
         << snacks[2].name;
}

考點：創建結構數組。

---

7.

// 4_13_7.cpp -- exercise 4.13.7
#include <iostream>

int main()
{
    using namespace std;

    struct Pizza_info
    {
        string name;
        int diameter;
        float weights;
    };

    Pizza_info cus_pizza;
    cout << "Please tell me the brand of your pizza: ";
    getline(cin, cus_pizza.name);
    cout << "Please chose the diameter of your pizza: ";
    cin >> cus_pizza.diameter;
    cout << "Please chose the weight of your pizza: ";
    cin >> cus_pizza.weights;
    cout << "Okay,your pizza is " << cus_pizza.name
         << " and the diameter of it is " << cus_pizza.diameter
         << ".The pizza's weight is " << cus_pizza.weights << "." << endl;

    return 0;
}

考點，創建一個結構變量，然後再通過訪問結構的成員來賦值。

---

8.

// 4_13_8.cpp -- exercise 4.13.8
#include <iostream>
#include <string>

struct pizza_info
{
    std::string name;
    int diameter;
    float weights;
};


int main()
{
    using namespace std;

    pizza_info *ps = new pizza_info;

    cout << "How big of the pizza do you want?" << endl;
    cin >> (*ps).diameter;
    cin.get(); // very important! C++ Primer Plus page 81!!!
    cout << "Okay, which brand are you prefer?"<< endl;
    getline(cin, ps->name);
    cout << "And tell me the weight of the pizza." << endl;
    cin >> ps->weights;
    cout << "Your pizza is " << (*ps).name << " and the diameter of it is "
         << ps->diameter << " and it weights " << ps->weights << endl;

    return 0;
}

這道題之所以標紅，是因爲我在先輸入披薩的尺寸後，沒等我輸入名稱就直接跳到輸入重量那裏了。最後認真讀書之後發現再C++PP第六版81頁有寫，cin在讀取用戶輸入的數字時，將回車生成的換行符留在輸入隊列中。因此加入一句cin.get(),跳過這個換行符就好了。

---

9.

//4_13_9.cpp -- exercise 4.13.9
#include<iostream>

struct CandyBar
{
    std::string name;
    float weights;
    int calorie;
};

int main()
{
    using namespace std;

    CandyBar *ps = new CandyBar[3]
    {
        {"One", 3.5, 20},
        {"Two", 3.6, 21},
        {"Three", 3.7, 22},
    };

    cout << "Names of snacks are:" << ps[0].name << " " << ps[1].name << " "
         << ps[2].name << endl;
    cout << "Weights of snacks are:" << ps[0].weights << " " << ps[1].weights << " "
         << ps[2].weights << endl;
    cout << "Calorie of snacks are:" << ps[0].calorie << " " << ps[1].calorie << " "
         << ps[2].calorie << endl;
}

考察用new來動態分配結構數組。（自己做的很不熟練）

---

10.

// 4_13_10.cpp -- exercise 4.13.10

#include <iostream>
#include <array>

int main()
{
    using namespace std;

    array<double, 3>  run_grade;
    cout << "Please enter your 1st time of 100m running:" << endl;
    double fst_time;
    cin >> fst_time;
    run_grade[0] = fst_time;
    cout << "Please enter your 2ed time of 100m running:" << endl;
    double snd_time;
    cin >> snd_time;
    run_grade[1] = snd_time;
    cout << "Please enter your 3rd time of 100m running:" << endl;
    double trd_time;
    cin >> trd_time;
    run_grade[2] = trd_time;

    double avg_time;
    avg_time = (fst_time + snd_time + trd_time) / 3;
    cout << "After 3 times running,your average time is:" << avg_time << endl;

    return 0;
}

考察array的創建，賦值以及訪問。