【第六章】分支语句和逻辑运算符

• get()方法读取一个字符，使用getline()来读取一行字符。

1.编写一个程序，读取键盘输入，直到遇到@符号为止，并回显输入（数字除外），同时将大写字符转换为小写字符，将小写字符转换为大写（别忘了cctype函数系列）

#include <iostream>
#include<cctype>
using namespace std;int main()
{cout << "请输入字符（‘@’停止）:";char input;cin.get(input);  // 从输入读取一个字符while (input != '@'){if (islower(input)){input = toupper(input);}else if (isupper(input)){input = tolower(input);}else if (isdigit(input)){cin.get(input); // 读取下一个字符，忽略数字continue;}// 输出转换后的字符cout << input;// 再次读取一个字符cin.get(input);}cout << endl;system("pause");return 0;
}

2.编写一个程序，最多将10个donation值读入一个double数组中（如果你愿意，也可以使用模板类array）。程序遇到非数字输入时将结束输入，并报告这些数字的平均值以及数组中有多少个数字大于平均值。

#include <iostream>
#include <array>
using namespace std;int main()
{array<double, 10> donation;double input;int count = 0;double sum = 0, avg = 0;cout << "请输入10个数字(输入非数字结束):";for (int i = 0; (i < 10) && (cin >> input); i++){donation[i] = input;count++;sum += donation[i];}avg = sum / count;int large = 0;for (int i = 0; i < count; i++){if (donation[i] > avg){large++;}}cout << "平均值：" << avg << "数组中有" << large << "个数字大于平均值" << endl;system("pause");return 0;
}

3.编写一个菜单驱动程序的雏形。该程序显示一个提供四个选项的菜单–每个选项用一个字母表标记。如果用户使用有效选项之外的字母进行响应，程序将提示用户输入有效的字母，直到用户这样选择为止。然后，该程序使用一条switch语句，根据用户的选择执行一个简单操作。该程序的运行情况如下：

Please enter one of the following choices:
c) carnivore         p) pianist
t) tree              g) game
f
Please enter a c,p,t or g:q
Please enter a c,p,t or g:t
A maple is a tree.

#include <iostream>
using namespace std;int main()
{cout << "Please enter one of the following choices:" << endl;cout << "c) carnivore         p) pianist" << endl;cout << "t) tree              g) game" << endl;char choices;cin.get(choices);while (choices != 'c' && choices != 'p' && choices != 't' && choices != 'g'){cin.get();cout << "Please enter a c,p,t or g:";cin.get(choices);}switch (choices){case 'c':break;case 'p':break;case 't':cout << "对了！" << endl;break;case 'g':break;}system("pause");return 0;
}

4.加入Benevolent Order of Programmer后，在BOP大会上，人们便可以通过加入者的真实姓名、头衔或秘密BOP姓名来了解他（她）。请编写一个程序，可以使用真实姓名、头衔、秘密姓名或成员偏好来列出成员。编写该程序时，请使用下面的结构：

//Benevolent Order of Programmers name structure
struct bop{char fullname[strsize];     //real namechar title[strzie];              //job titlechar bopname[strsize];   //secret BOP nameint preference;                //0=fullname,1=title,2=bopname
};

该程序创建一个由上述结构组成的小型数组，并将其初始化为适当的值。另外，该程序使用一个循环，让用户在下面的选项中进行选择：

a.display by name        b.diaplay by title
c.display by bopname     d.display by preference
q.quit

注意，“display by preference”并不意味显示成员的偏好，而是意味着根据成员的偏好来列出成员。例如，如果偏好号为1，则选择d将显示程序员的头衔。该程序的运行情况如下：

Benevolent Order of Programmers Report
a. display by name         b. display by title
c. display by bopname      d. display by preference
q. quit
Enter your choice: a
Wimp Macho
Raki Rhodes
Celia Laiter
Hoppy Hipman
Pat Hand
Next choice: d
Wimp Macho
Junior Programmer
MIPS
Analyst Trainee
LOOPY
Next choice: q
Bye!

代码

#include <iostream>
using namespace std;const int structsize = 40;
struct bop {char fullname[structsize];     //real namechar title[structsize];              //job titlechar bopname[structsize];   //secret BOP nameint preference;                //0=fullname,1=title,2=bopname
};
bop user[] = {{"even taylor","engineer","Ping",0},{"niko tr","juni oop","",1},{"celina hup","","MIPS",2},{"sasiuciu","","Loop",2},
};
const int len = sizeof(user) / sizeof(user[0]);void print_by_name();
void print_by_title();
void print_by_bopname();
void print_by_pref();int main()
{cout << "Benevolent Order of Programmers Report" << endl;cout << "a. display by name          b. display by title" << endl;cout << "c. display by bopname       d. display by preference" << endl;cout << "q. quit" << endl;cout << "Enter your choice: ";char choices;cin.get(choices);while (choices != 'q'){switch (choices){case 'a':print_by_name();break;case 'b':print_by_title();break;case 'c':print_by_bopname();break;case 'd':print_by_pref();break;default:cout << "请输入a、b、c、d:";break;}cin.get();cout << "请输入你的下一个选项:";cin.get(choices);}system("pause");return 0;
}void print_by_name() {for (int i = 0; i < len; i++){cout << user[i].fullname << endl;}
}void print_by_title() {for (int i = 0; i < len; i++){cout << user[i].title << endl;}
}void print_by_bopname() {for (int i = 0; i < len; i++){cout << user[i].bopname << endl;}
}void print_by_pref() {for (int i = 0; i < len; i++){if (user[i].preference == 0){cout << user[i].fullname << endl;}else if (user[i].preference == 1){cout << user[i].title << endl;}else{cout << user[i].bopname << endl;}}
}

5.在Neutronia王国,货币单位是tvarp,收入所得税的计算方式如下:

5000 tvarps: 不收税
5001－15000 tvarps: 10%
15001－35000 tvarps: 15%
35000 tvarps以上: 20%

例如,收入为38000 tvarps时,所得税为5000×0.00+10000×0.10+2000×0.15+3000×0.20,即 4600tvarps。请编写一个程序，使用循环来要求用户输入收入，并报告所得税，当用户输入负数或非数字时，循环将结束。

#include <iostream>
using namespace std;int main()
{cout << "请输入收入(负数或者非数字结束):";double income;double tax;while (cin >> income){if (income > 35000){tax = 10000 * 0.10 + 20000 * 0.15 + (income - 35000) * 0.20;}else if (income >= 15001){tax = (income - 3500) * 0.15 + 10000 * 0.10;}else if (income >= 5001){tax = (income - 5000) * 0.10;}else if (income >= 0){tax = 0;}else{cout << "请输入正确数字" << endl;break;}cout << "你的所得税为：" << tax << " tvarps" << endl;cout << "请输入收入(负数或者非数字结束):";}system("pause");return 0;
}

6.编写一个程序，记录捐助给"维护合法权利团体"的资金。该程序要求用户输入捐赠者数目，然后要求用户输入每一个捐献者的姓名和款项。这些信息被存储在一个动态分配的结构数组中.每个数据结构有两个成员：用来存储姓名的字符串数组(或string对象)和用来存储款项的double成员。读取所有的数据后,程序将显示所有捐款超过10000的捐款着姓名及其捐款数额。该列表前应包含一个标题,指出下面的捐款者是重要捐款人(Grand Patrons)。然后,程序将列出其他的捐款者，该列表要以Partons开头。如果某种类别没有捐款者，则程序将打印单词"none"。该程序只显示这两种类别，而不进行排序。

#include <iostream>
#include <string>
using namespace std;struct Donation
{string name;    //姓名double fund;    //捐款数额
};void display(Donation* p, int patrona_number, bool isGrandPatrons);int main()
{cout << "How many patrons? ";int patrona_number;cin >> patrona_number;cin.get();//建立动态数组Donation* p = new Donation[patrona_number];cout << "Starting to input patrons' info:" << endl;int id = 0;while (id < patrona_number){cout << "Enter the name of patrons:";getline(cin, p[id].name);cout << "Enter the fund of " << p[id].name << " :";cin >> p[id].fund;cin.get();id++;cout << "Continue to input,or press(f)to finished.";if (cin.get() == 'f'){break;}}cout << "******Grand Partons******" << endl;display(p, patrona_number, true);cout << "******Partons******" << endl;display(p, patrona_number, false);system("pause");return 0;
}void display(Donation* p, int patrona_number, bool isGrandPatrons) {int num = 0;for (int i = 0; i < patrona_number; i++){if (isGrandPatrons) {if (p[i].fund > 10000){num++;cout << p[i].name << endl;}}else{if (p[i].fund <= 10000){num++;cout << p[i].name << endl;}}}if (num == 0) {cout << "none" << endl;}
}

7.编写一个程序,它每次读取一个单词，直到用户只输入q。然后,该程序指出有多少个单词以元音打头，有多少个单词以辅音打头，还有多少个单词不属于这两类。为此，方法之一是，使用isalpha()来区分以字母和其他字母打头的单词，然后对于通过isalpha()测试的单词，使用if或switch语句来确定哪些以元音打头。该程序的运行情况如下：

Enter words (q to quit):
The 12 awesome oxem ambled
quiety across 15 meters of lawn. q
5 words beginning with vowels
4 words beginning with consonants
2 others

#include <iostream>
#include <string>
using namespace std;int main()
{char words;cout << "Enter words (q to quit):" << endl;int other = 0; //记录其他个数int num = 0;//记录元音个数int count = 0; //记录非元音个数while (cin >> words){if (words == 'q'){break;}else{if (isalpha(words)){switch (words){case 'a':case 'e':case 'i':case 'o':case 'u':num++;break;default:count++;break;}}else{other++;}}}cout << num << " words beginning with vowels" << endl;cout << count << " words beginning with consonants" << endl;cout << other << " others" << endl;system("pause");return 0;
}

8.编写一个程序，他打开一个文件，逐个字地读取该文件，直到到达文件末尾，然后指出该文件中包含多少个字符。

#include <iostream>
#include <fstream>
#include <string>
using namespace std;int main()
{ifstream stream;string file_name;cout << "Enter the file name: ";getline(cin, file_name);// 通过文件流打开文件、如果打开失败则终止stream.open(file_name);if (!stream.is_open()){cout << "Error to open file." << endl;exit(1);}char read_char;int count = 0;// efo()判断是否到达文件末尾while (!stream.eof()){stream >> read_char;count++;}cout << file_name << "文件一共有" << count << "字符" << endl;//关闭文件流stream.close();system("pause");return 0;
}

9.完成编程练习6，但从文件中读取所需的信息。该文件的第一项应为捐款人数，余下的内容应为对的行。在每一对中，第一行为捐款人姓名，第二行为捐款数额。

#include <iostream>
#include <fstream>
#include <string>
using namespace std;struct Donation
{string name;    //姓名double fund;    //捐款数额
};void display(Donation* p, int patrona_number, bool isGrandPatrons);int main()
{ifstream fin;fin.open("09.txt", ios::in);if (!fin.is_open()) {cout << "Error to open file." << endl;exit(1);}int number = 0;fin >> number; //读取人数fin.get();if (number <= 0){exit(1);}//动态数组Donation* p = new Donation[number];//循环读取捐款人信息cout << "******读取文件信息******" << endl;for (int i = 0; i < number; i++){getline(fin, p[i].name);fin >> p[i].fund;fin.get();cout << p[i].name << " -> " << p[i].fund << endl;}cout << "******Grand Partons******" << endl;display(p, number, true);cout << "******Partons******" << endl;display(p, number, false);system("pause");return 0;
}void display(Donation* p, int patrona_number, bool isGrandPatrons) {int num = 0;for (int i = 0; i < patrona_number; i++){if (isGrandPatrons) {if (p[i].fund > 10000){num++;cout << p[i].name << endl;}}else{if (p[i].fund <= 10000){num++;cout << p[i].name << endl;}}}if (num == 0) {cout << "none" << endl;}
}