C++ primer Plus（第六版）中文版 第四章 复合类型 编程练习答案
第四章 编程练习
1. 编写一个小程序，如下述输出示例的那样请求并显示信息：
What is your first name? Betty 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。
1.1 C风格字符串版
#include
int main()
{
using namespace std;
const int size = 30;
char first_name[size];
char last_name[size];
unsigned int age;
char grade;
cout << "What is your first name? ";
cin.getline(first_name,size); //或用cin.get(first_name,size).get();
cout << "What is your last name? ";
cin.getline(last_name,size); //或用cin.get(last_name,size).get();
cout << "What letter grade do you deserve? ";
cin >> grade; //cin将键盘输入的char类型的grade字符转换为对应的ASCII码
grade += 1; //ASCII码+1
cout << "what is your age? ";
cin >> age;
cout << "Name: " << last_name << ", " << first_name << endl;
cout << "Grade: " << grade << endl; //cout将ASCII码转换为字符
cout << "Age: " << age << endl;
return 0;
}
//或者
#include
int main()
{
using namespace std;
const int size = 30;
char first_name[size];
char last_name[size];
unsigned int age;
char grade;
cout << "What is your first name? ";
cin.getline(first_name,size);
cout << "What is your last name? ";
cin.getline(last_name,size);
cout << "What letter grade do you deserve? ";
cin >> grade; //cin将键盘输入的char类型的grade字符转换为对应的ASCII码
cout << "what is your age? ";
cin >> age;
cout << "Name: " << last_name << ", " << first_name << endl;
cout << "Grade: " << char(grade+1) << endl;
//char类型的grade与int型的1做加法运算时，自动提升为int型，grade+1的结果为int型
//char(grade+1)强制类型转换为char类型
//cout将ASCII码转换为字符
cout << "Age: " << age << endl;
return 0;
}
1.2 string类版
#include
#include
int main()
{
using namespace std;
const int size = 30;
string first_name;
string last_name;
unsigned int age;
char grade;
cout << "What is your first name? ";
getline(cin, first_name);
cout << "What is your last name? ";
getline(cin, last_name);
cout << "What letter grade do you deserve? ";
cin >> grade; //cin将键盘输入的char类型的grade字符转换为对应的ASCII码
grade += 1; //ASCII码+1
cout << "what is your age? ";
cin >> age;
cout << "Name: " << last_name << ", " << first_name << endl;
cout << "Grade: " << grade << endl; //cout将ASCII码转换为字符
cout << "Age: " << age << endl;
return 0;
}
1.3 动态字符串数组版
#include
#include
int main()
{
using namespace std;
const int size = 30;
char first_name[size];
char last_name[size];
unsigned int age;
char grade;
cout << "What is your first name? ";
cin.getline(first_name,size);
cout << "What is your last name? ";
cin.getline(last_name,size);
cout << "What letter grade do you deserve? ";
cin >> grade;
grade += 1;
cout << "what is your age? ";
cin >> age;
char* firstname = new char [strlen(first_name)+1];
char* lastname = new char [strlen(last_name)+1];
strcpy(firstname, first_name);
strcpy(lastname, last_name);
cout << "Name: " << lastname << ", " << firstname << endl;
cout << "Grade: " << grade << endl;
cout << "Age: " << age << endl;
delete [] firstname;
delete [] lastname;
return 0;
} 1.4 动态字符串数组+函数版
#include
#include
char* getname(char*);
int main()
{
using namespace std;
const int size = 30;
char first_name[size];
char last_name[size];
unsigned int age;
char grade;
cout << "What is your first name? ";
cin.getline(first_name,size);
cout << "What is your last name? ";
cin.getline(last_name,size);
cout << "What letter grade do you deserve? ";
cin >> grade;
grade += 1;
cout << "what is your age? ";
cin >> age;
cout << "Name: " << getname(last_name) << ", " << getname(first_name) << endl;
cout << "Grade: " << grade << endl;
cout << "Age: " << age << endl;
delete [] getname(last_name);
return 0;
}
char* getname(char* name)
{
char* name_new = new char [strlen(name)+1];
strcpy(name_new, name);
return name_new;
}
2. 修改程序清单4.4， 使用C++ string类而不是char数组，程序4.4如下
//程序4.4如下
// instr2.cpp -- reading more than one word with getline
#include
int main()
{
using namespace std;
const int ArSize = 20;
char name[ArSize];
char dessert[ArSize];
cout << "Enter your name:\n";
cin.getline(name, ArSize); // reads through newline
cout << "Enter your favorite dessert:\n";
cin.getline(dessert, ArSize);
cout << "I have some delicious " << dessert;
cout << " for you, " << name << ".\n";
// cin.get();
return 0;
} 修改后
#include
#include
int main()
{
using namespace std;
const int ArSize = 20;
string name;
string dessert;
cout << "Enter your name:\n";
getline(cin, name);
cout << "Enter your favorite dessert:\n";
getline(cin, dessert);
cout << "I have some delicious " << dessert;
cout << " for you, " << name << ".\n";
return 0;
} 3. 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一个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
3.1 strcpy版
#include
#include
int main()
{
using namespace std;
const int size=30;
char first_name[size];
char last_name[size];
char divide[size] = ", ";
char full_name[size];
cout << "Enter your first name: ";
cin.get(first_name, 30).get();
cout << "Enter your last name: ";
cin.get(last_name, 30).get();
strcpy(full_name, strcat(last_name, strcat(divide, first_name)));
cout << "Here's the information in a single string: ";
cout << full_name;
return 0;
}
3.2 指针版
#include
#include
int main()
{
using namespace std;
const int size=30;
char first_name[size];
char last_name[size];
char divide[size] = ", ";
char* full_name;
cout << "Enter your first name: ";
cin.get(first_name, 30).get();
cout << "Enter your last name: ";
cin.get(last_name, 30).get();
full_name = strcat(last_name, strcat(divide, first_name));
//或者用
//full_name = strcat(divide, first_name);
//full_name = strcat(last_name, full_name);
cout << "Here's the information in a single string: ";
cout << full_name;
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。
下面是该程序运行的情形：
Enter your first name: Flip
Enter your last name: Fleming
Here's the information in a single string: Fleming, Flip
4.1 基础版
#include
#include
int main()
{
using namespace std;
string first_name;
string last_name;
string divide = ", ";
string full_name;
cout << "Enter your first name: ";
getline(cin, first_name);
cout << "Enter your last name: ";
getline(cin, last_name);
full_name = last_name + divide + first_name;
cout << "Here's the information in a single string: ";
cout << full_name;
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。
5.1 基础版
#include
struct CandyBar
{
char brand[20];
double weight;
int calorie;
};
int main()
{
using namespace std;
CandyBar snack = {"Mocha Munch", 2.3, 350};
cout << "The brand is " << snack.brand << endl;
cout << "The weight is " << snack.weight << endl;
cout << "The calorie is " << snack.calorie << endl;
return 0;
}
5.2 同时完成定义结构和创建结构变量并初始化，省略=号
#include
struct CandyBar
{
char brand[20];
double weight;
int calorie;
};
int main()
{
using namespace std;
struct CandyBar
{
char brand[20];
double weight;
int calorie;
}snack{"Mocha Munch", 2.3, 350};
cout << "The brand is " << snack.brand << endl;
cout << "The weight is " << snack.weight << endl;
cout << "The calorie is " << snack.calorie << endl;
return 0;
} 5.3 使用动态结构
#include
#include
struct CandyBar
{
std::string brand; //下面涉及到赋值，所以不能用C风格字符串
double weight;
int calorie;
};
int main()
{
using namespace std;
CandyBar* snack = new CandyBar;
snack->brand = "Mocha Munch"; //或者用(*snack).brand = "Mocha Munch";
snack->weight = 2.3; //或者用(*snack).weight = 2.3;
snack->calorie = 350; //或者用(*snack).calorie = 2.3;
cout << "The brand is " << snack->brand << endl;
cout << "The weight is " << snack->weight << endl;
cout << "The calorie is " << snack->calorie << endl;
delete snack;
return 0;
} 6. 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。
6.1 基础版
#include
struct CandyBar
{
char brand[20];
double weight;
int calorie;
};
int main()
{
using namespace std;
CandyBar candy[3]=
{
{"Mocha Munch", 2.3, 350},
{"Doublemint", 5.0, 400},
{"White Rabbit", 3.5, 200},
};
cout << "The first brand is " << candy[0].brand << endl;
cout << "The first weight is " << candy[0].weight << endl;
cout << "The first calorie is " << candy[0].calorie << endl << endl;
cout << "The second brand is " << candy[1].brand << endl;
cout << "The second weight is " << candy[1].weight << endl;
cout << "The second calorie is " << candy[1].calorie << endl << endl;
cout << "The third brand is " << candy[2].brand << endl;
cout << "The third weight is " << candy[2].weight << endl;
cout << "The third calorie is " << candy[2].calorie << endl << endl;
return 0;
} 6.2 for 循环版
#include
struct CandyBar
{
char brand[20];
double weight;
int calorie;
};
int main()
{
using namespace std;
CandyBar candy[3]=
{
{"Mocha Munch", 2.3, 350},
{"Doublemint", 5.0, 400},
{"White Rabbit", 3.5, 200},
};
for(int i=0; i<3; i++)
{
cout << "The " << i+1 << " brand is " << candy[i].brand << endl;
cout << "The " << i+1 << " weight is " << candy[i].weight << endl;
cout << "The " << i+1 << " calorie is " << candy[i].calorie << endl << endl;
}
return 0;
} 7. William Wingate 从事披萨饼分析服务。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）披萨饼的重量
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（或它的方法）和cout
7.1 基础版
#include
struct PizzaAnalyze
{
char brand[20];
double diameter;
double weight;
};
int main()
{
using namespace std;
PizzaAnalyze pizza;
cout << "请输入披萨饼公司名称：";
cin.get(pizza.brand,20).get();
cout << "请输入披萨饼的直径：";
cin >> pizza.diameter;
cout << "请输入披萨饼的重量：";
cin >> pizza.weight;
cout << "披萨饼公司名称：" << pizza.brand << endl;
cout << "披萨饼的直径：" << pizza.diameter << endl;
cout << "披萨饼的重量：" << pizza.weight << endl;
return 0;
}
7.2 动态结构数组+for+函数实现多次输入版
#include
struct PizzaAnalyze
{
char brand[20];
double diameter;
double weight;
};
void input(PizzaAnalyze*, int);
void output(PizzaAnalyze*, int);
int main()
{
using namespace std;
int num;
cout << "请输入披萨的总数：";
cin >> num;
cin.get();
PizzaAnalyze* pizza = new PizzaAnalyze [num];
input(pizza, num);
output(pizza, num);
delete [] pizza;
return 0;
}
void input(PizzaAnalyze* pizza, int num)
{
using namespace std;
for (int i=0; i> pizza[i].diameter;
cin.get();
cout << "请输入披萨饼的重量：";
cin >> pizza[i].weight;
cin.get();
cout << "\n";
}
}
void output(PizzaAnalyze* pizza, int num)
{
using namespace std;
for (int i=0; i 8. 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披萨饼的直径。
#include
struct PizzaAnalyze
{
char brand[20];
double diameter;
double weight;
};
int main()
{
using namespace std;
PizzaAnalyze* pizza = new PizzaAnalyze;
cout << "请输入披萨饼的直径：";
cin >> (*pizza).diameter;
cin.get();
cout << "请输入披萨饼公司名称：";
cin.get((*pizza).brand,20).get();
cout << "请输入披萨饼的重量：";
cin >> (*pizza).weight;
cout << "披萨饼公司名称：" << (*pizza).brand << endl;
cout << "披萨饼的直径：" << (*pizza).diameter << endl;
cout << "披萨饼的重量：" << (*pizza).weight << endl;
delete pizza;
return 0;
}
9. 完成编程练习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
9.1 基础版
#include
struct CandyBar
{
char brand[20];
double weight;
int calorie;
};
int main()
{
using namespace std;
int size = 3;
CandyBar* candy = new CandyBar [size];
candy[0] = {"Mocha Munch", 2.3, 350};
candy[1] = {"Doublemint", 5.0, 400};
candy[2] = {"White Rabbit", 3.5, 200};
cout << "The first brand is " << candy[0].brand << endl;
cout << "The first weight is " << candy[0].weight << endl;
cout << "The first calorie is " << candy[0].calorie << endl << endl;
cout << "The second brand is " << candy[1].brand << endl;
cout << "The second weight is " << candy[1].weight << endl;
cout << "The second calorie is " << candy[1].calorie << endl << endl;
cout << "The third brand is " << candy[2].brand << endl;
cout << "The third weight is " << candy[2].weight << endl;
cout << "The third calorie is " << candy[2].calorie << endl << endl;
delete [] candy;
return 0;
} 9.2 for循环版
#include
struct CandyBar
{
char brand[20];
double weight;
int calorie;
};
void output(CandyBar*);
int main()
{
using namespace std;
int size = 3;
CandyBar* candy = new CandyBar [size];
candy[0] = {"Mocha Munch", 2.3, 350};
candy[1] = {"Doublemint", 5.0, 400};
candy[2] = {"White Rabbit", 3.5, 200};
output(candy);
return 0;
}
void output(CandyBar* candy)
{
using namespace std;
for(int i=0; i<3; i++)
{
cout << "The " << i+1 << " brand is " << candy[i].brand << endl;
cout << "The " << i+1 << " weight is " << candy[i].weight << endl;
cout << "The " << i+1 << " calorie is " << candy[i].calorie << endl << endl;
}
}
10. 编写一个程序，让用户输入三次40码跑的成绩（如果您愿意，也可以让用户输入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。
10.1 基础版
#include
#include
int main()
{
using namespace std;
const int num = 3;
array time;
double average;
cout << "请输入第1次40米跑的成绩：";
cin >> time[0];
cout << "请输入第2次40米跑的成绩：";
cin >> time[1];
cout << "请输入第3次40米跑的成绩：";
cin >> time[2];
average = (time[0] + time[1] + time[2]) / num;
cout << "第一次的成绩为：" << time[0] << endl;
cout << "第二次的成绩为：" << time[1] << endl;
cout << "第三次的成绩为：" << time[2] << endl;
cout << num << "次的平均成绩为" << average << endl;
return 0;
}
10.1 for循环版
#include
#include
int main()
{
using namespace std;
const int num = 3;
array time;
double average = 0;
for(int i=0; i < num; i++)
{
cout << "请输入第" << i+1 <<"次40米跑的成绩：";
cin >> time[i];
}
for(int i=0; i < num; i++)
average = average + time[i];
average = average / num;
for(int i=0; i < num; i++)
cout << "第" << i+1 <<"次的成绩为：" << time[i] << endl;
cout << num << "次的平均成绩为" << average << endl;
return 0;
}
10.2 for循环+函数版
#include
#include
using namespace std;
const int num = 3;
array time;
array input(array time, const int num);
double calculate_average(array time, const int num);
void output(arraytime, const int num, double average);
int main()
{
double average;
time = input(time, num);
average = calculate_average(time, num);
output(time, num, average);
return 0;
}
array input(array time, const int num)
{
using namespace std;
for(int i=0; i < num; i++)
{
cout << "请输入第" << i+1 <<"次40米跑的成绩：";
cin >> time[i];
}
return time;
}
double calculate_average(array time, const int num)
{
double average = 0;
for(int i=0; i < num; i++)
average = average + time[i];
average = average / num;
return average;
}
void output(array time, const int num, double average)
{
for(int i=0; i < num; i++)
cout << "第" << i+1 <<"次的成绩为：" << time[i] << endl;
cout << num << "次的平均成绩为" << average << endl;
}