c++ primer plus 编程答案上

第二章
第三章
第四章
第五章
第六章

第二章

编写一个c++程序，它显示您的姓名和地址

#include<iostream>
int main() {using namespace std;cout << "my name is xxx,\nmy address is xxx" << endl;return 0;
}

编写一个c++程序，他要求用户输入一个以long为单位的距离，然后将她转化为为码。

#include <iostream>int main() {using namespace std;int distance = 0, yard;cout << "Please input a distance numebr in the unit of Long: ";cin >> distance;yard = distance * 220;cout << "The distance tranform in yards is: " << yard << endl;return 0;
}

编写一个C++程序，它使用 3 个用户定义的函数（包括main()），并生成下面的输出：


Three blind mice
Three blind mice
See how they run
See how they run

其中一个函数要调用两次，该函数生成前两行；另一个函数也被调用两次，并生成其余的输出。

#include <iostream>using namespace std;void blind_mice() {cout << "Three blind mice." << endl;return;
}void how_they_run() {cout << "See how they run" << endl;return;
}int main() {blind_mice();blind_mice();how_they_run();how_they_run();return 0;
}

编写一个程序，让用户输入其年龄，然后显示该年龄包含多少个月，如下所示：

Enter your age: 29

#include <iostream>int main() {using namespace std;int years, months;cout << "Enter your age: ";cin >> years;months = years * 12;cout << years << " years is " << months << " monthes." << endl;  return 0;
}

编写一个程序，其中的main( )调用一个用户定义的函数（以摄氏温度值为参数，并返回相应的华氏温度值）。该程序按下面的格式要求用户输入摄氏温度值，并显示结果：

Please enter a Celsius value: 2020 degrees Celsius is 68 degrees Fahrenheit.

转换公式：华氏温度 = 1.8×摄氏温度 + 32.0

#include <iostream>double celsiu2fahrenit(double celsius) {return 1.8 * celsius + 32.0;
}int main() {using namespace std;double celsius;cout << "Please enter a celsius value: ";cin >> celsius;cout << celsius << " degrees Celsius is " << celsiu2fahrenit(celsius) << " degrees Fahrenheit." << endl;return 0;
}

编写一个程序，其main( )调用一个用户定义的函数（以光年值为参数，并返回对应天文单位的值）。该程序按下面的格式要求用户输入光年值，并显示结果：

Enter the number of light years: 4.24.2 light years = 265608 astromonical units.

天文单位是从地球到太阳的平均距离（约150000000公里或93000000英里），光年是光一年走的距离（约10万亿公里或6万亿英里）（除太阳外，最近的恒星大约离地球4.2光年）。请使用double类型，转换公式为：1光年=63240天文单位.

#include <iostream>double light_years2astromonical_unit(double light_years) {return light_years * 63240;
}int main() {using namespace std;double light_years;cout << "nter the number of light years: ";cin >> light_years;cout << light_years << " light years = " << light_years2astromonical_unit(light_years)<< " astromonical units." << endl;return 0;
}

7.编写一个程序，要求用户输入小时数和分钟数。在 main() 函数中，将这两个值传递给一个void函数，后者以下面这样的格式显示这两个值：

Enter the number of hours: 9
Enter the number of minutes: 28Time: 9:28

#include <iostream>using namespace std;void display_time(double hours, double minutes) {cout << "Time: " << hours << ":" << minutes << endl;}int main() {    double hours, minutes;cout << "Enter the number of hours: ";cin >> hours;cout << "Enter the number of minutes: ";cin >> minutes;display_time(hours, minutes);return 0;
}

第三章

编写一个小程序，要求用户使用一个整数指出自己的身高（单位为英寸），然后将身高转换为英尺和英寸。该程序使用下划线字符来指示输入位置。另外，使用一个const符号常量来表示转换因子。

#include <iostream>const int Foot2inch = 12;int main() {using namespace std;int input_height = 0;cout << "Please input you height in inch: __\b\b";cin >> input_height;int height_foot = input_height / Foot2inch;int height_inch = input_height % Foot2inch;cout << "Your height in inch is: " << input_height << "; transforming in foot and inch is: " << height_foot << " foot "<< height_inch << " inch." << endl;return 0;
}

 编写一个小程序，要求以几英尺几英寸的方式输入其身高，并以磅为单位输入其体重。（使用3个变量来存储这些信息。）该程序报告其BMI（Body Mass Index，体重指数）。为了计算BMI，该程序以英寸的方式指出用户的身高（1英尺为12英寸），并将以英寸为单位的身 高转换为以米为单位的身高（1英寸=0.0254米）。然后，将以磅为单位 的体重转换为以千克为单位的体重（1千克=2.2磅）。最后，计算相应的BMI—体重（千克）除以身高（米）的平方。用符号常量表示各种转 换因子。


#include <iostream>const int Foot2Inch = 12;
const double Inch2Meter = 0.0254;
const double Kg2Pound = 2.2;double BMI(double weight, double height) {return weight/(height*height);
}int main() {using namespace std;double height_foot = 0;double height_inch = 0;double weight_pound = 0;cout << "Please enter your height in foot and Inch2Meter." << endl;cout << "Enter the foot of height: __\b\b";cin >> height_foot;cout << "Enter the inch of height: __\b\b";cin >> height_inch;cout << "Please enter your weight in pound: __\b\b";cin >> weight_pound;double height_meter = (height_foot * Foot2Inch + height_inch) * Inch2Meter;double weight_kg = weight_pound / Kg2Pound;double bmi = BMI(weight_kg, height_meter);cout << "Your BMI is: " << bmi << endl;return 0;
}

编写一个程序，要求用户以度、分、秒的方式输入一个纬度，然后以度为单位显示该纬度。1度为60分，1分等于60秒，请以符号常量的方式表示这些值。对于每个输入值，应使用一个独立的变量存储它。下面是该程序运行时的情况：


#include <iostream>int main() {using namespace std;double degree, minutes, seconds;cout << "Enter a latitude in degree, minutes and seconds." << endl;cout << "First, enter the degree: ";cin >> degree;cout << "Next, enter the minutes of arc: ";cin >> minutes;cout << "Finally, enter the seconds of arc: ";cin >> seconds;double degree2 = degree + minutes/60 + seconds/3600;cout << degree << " degrees, " << minutes << " minutes, "<< seconds << " seconds = " << degree2 << endl;return 0;
}

编写一个程序，要求用户以整数方式输入秒数（使用long或long long变量存储），然后以天、小时、分钟和秒的方式显示这段时间。使用符号常量来表示每天有多少小时、每小时有多少分钟以及每分钟有多少秒。该程序的输出应与下面类似：

Enter the number of seconds: 31600000
31600000 seconds = 365 days, 17 hours, 46 minutes, 40 seconds.

#include <iostream>int main() {using namespace std;long total_seconds;cout << "Enter the number of seconds: ";cin >> total_seconds;int days = total_seconds / 86400;int hours = (total_seconds % 86400) / 3600;int minutes = ((total_seconds % 86400) % 3600) / 60;int seconds = ((total_seconds % 86400) % 3600) % 60;cout << total_seconds << "seconds = " << days << " days, " << hours << " hours, "<< minutes << " minutes, "<< seconds << " seconds." << endl;return 0;
}

编写一个程序，要求用户输入全球当前的人口和中国当前的人口（或其他国家的人口）。将这些信息存储在long long变量中，并让程序显示中国（或其他国家）的人口占全球人口的百分比。该程序的输出应与下面类似：

Enter the world's population: 7850176700
Enther the population of China: 1411780000
The population of the China is 17.9841% of the world population.

#include <iostream>int main() {using namespace std;long long population_world, population_China;cout << "Enter the world's population: ";cin >> population_world;cout << "Enter the population of China: ";cin >> population_China;double rate = double(population_China)/population_world;cout << "The population of the China is " << rate * 100<< "% of the world population." << endl;return 0;
}

编写一个程序，要求用户输入驱车里程（英里）和使用汽油量（加仑），然后指出汽车耗油量为一加仑的里程。如果愿意，也可以让程序要求用户以公里为单位输入距离，并以升为单位输入汽油量，然后指出欧洲风格的结果—即每100公里的耗油量（升）。

#include <iostream>int main() {using namespace std;double kilometer, oil_liter;cout << "Enter the distance that you've dirver in kilometer: ";cin >> kilometer;cout << "Enter the comsumption of oil: ";cin >> oil_liter;double kilometer_per_liter = kilometer / oil_liter;cout << "The average fuel comsumption is " << 100 / kilometer_per_liter << " L/100km" << endl;
}

编写一个程序，要求用户按欧洲风格输入汽车的耗油量（每100公里消耗的汽油量（升）），然后将其转换为美国风格的耗油量—每加仑多少英里。

注意，除了使用不同的单位计量外，美国方法（距离/燃
料）与欧洲方法（燃料/距离）相反。100公里等于62.14英里，1加仑等于3.875升。因此，19mpg大约合12.4l/100km，27mpg大约合
8.71/100km。

#include <iostream>int main() {using namespace std;const double Km2Mile = 0.6214;const double Gallon2Litre = 3.875;double fuel_comsuption_en = 0.0;cout << "Enter the fuel comsuption in European standard: ";cin >> fuel_comsuption_en;double fuel_comsuption_us = (100 * Km2Mile) / (fuel_comsuption_en/Gallon2Litre);cout << "The fuel comsuption in US standard is " << fuel_comsuption_us << " Miles/Gallon (mpg)." << endl;  return 0;
}

第四章

题：编写一个程序，如下输出实例所示的请求并显示信息：

What is your first name? Betty Sue
Waht is your last name? Yewe
What letter grade do you deserve? B 
What is your age? 22Name: Yewe, Betty Sue
Grade: C 
Age: 22

程序应接受的名字包含多个单词。另外，程序将向下调整成绩。假设用户请求A、B或C，返回 B、C 或 D。

#include<iostream>
#include<string>int main() {using namespace std;char first_name[40];char last_name[40];char grade_letter;int age;cout << "What is your first name: ";cin.getline(first_name, 40);cout << "What is your last name: ";cin.getline(last_name, 40);cout << "What letter grade do you deserve: ";cin >> grade_letter;cout << "What is your age: ";cin >> age;cout << "Name: " << last_name << ", " << first_name << endl;cout << "Grade: " << char(grade_letter + 1) << endl;cout << "Age:" << age << endl;return 0;
}

题：修改程序清单4.4，使用 C++ string 类而不是 char 数组。

#include<iostream>
#include<string>int main() {using namespace std;string name;string dessert;cout << "Enter your name:" << endl;getline(cin, name);cout << "Enter your favorite dessert" << endl;getline(cin, dessert);cout << "I have delicious " << dessert;cout << " for you, " << name << "." << endl;return 0;
}

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

#include<iostream>
#include<string>
#include<cstring>int main() {using namespace std;char first_name[20], last_name[20];char final_name[50];cout << "Enter your last_name:";cin.getline(last_name, 20);cout << "Enter your first_name:";cin.getline(first_name, 20);strcpy(final_name, last_name);strcat(final_name, ",");strcat(final_name, first_name);cout << "Here's the information in a single string: " << final_name << endl;return 0;
}

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。下面是该程序运行时的情形：

Enter your first name: Flip
Enter your last name: Fleming
Here's the information in a single string: Fleming, Flip

#include<iostream>
#include<string>int main() {using namespace std;string first_name, last_name;string final_name;cout << "Enter your first name" << endl;getline(cin, first_name);cout << "Enter your last name" << endl;getline(cin, last_name);final_name = last_name + "," + first_name;cout << "Here's the information in a single string: " << final_name << endl;return 0;
}

结构体 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）。编写一个程序，声明这个结构体，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。

#include <iostream>
#include <string>struct CandyBar
{std::string name;double weight;int calories;
};int main() {using namespace std;CandyBar snack = { "Mocha Munch", 2.3, 350 };  // 初始化结构体cout << "The name of the CandyBar: " << snack.name << endl;cout << "The weight of the candy: " << snack.weight << endl;cout << "The calories information: " << snack.calories << endl;return 0;
}

结构体 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，然后显示每个结构体的内容。

#include <iostream>
#include <string>struct CandyBar
{std::string name;double weight;int calories;
};int main() {using namespace std;CandyBar candbar[3] = {{"Mocha Munch", 2.3, 350},{"Big Rabbit", 5, 300},{"Joy Boy", 4.1, 430}};cout << "The name of the CandyBar: " << candbar[0].name << endl;<< "The weight of the candy: " << candbar[0].weight << endl;<< "The calories information: " << candbar[0].calories << endl<<endl;cout << "The name of the CandyBar: " << candbar[1].name << endl;<< "The weight of the candy: " << candbar[1].weight << endl;<< "The calories information: " << candbar[1].calories << endl<<endl;cout << "The name of the CandyBar: " << candbar[2].name << endl;<< "The weight of the candy: " << candbar[2].weight << endl;<< "The calories information: " << candbar[2].calories << endl;return 0;
}

William Wingate从事比萨饼分析服务。对于每个披萨饼，他都需要记录下列信息：

披萨饼公司的名称，可以有多个单词组成；
披萨饼的直径；
披萨饼的重量。
请设计一个能够存储这些信息的结构体，并编写一个使用这种结构体变量的程序。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（或其它的方法）和cout。

#include <iostream>
#include <string>struct Pizza
{std::string company;double diameter;double weight;};int main() {using namespace std;Pizza pizza;cout << "Enter the pizza company: ";getline(cin, pizza.company);cout << "Enter the diameter of pizza: ";cin >> pizza.diameter;cout << "Enter the weight of pizza: ";cin >> pizza.weight;cout << "\nHere is the pizza information: "<<endl<< "Company: " << pizza.company << endl<< "Diameter: " << pizza.diameter << endl<< "Weight: " << pizza.weight << endl;return 0;
}

完成编程练习7，但使用 new 来为结构体分配内存，而不是声明一个结构体变量。另外，让程序在请求输入比萨饼公司名称之前输入比萨饼的直径。

#include <iostream>
#include <string>struct Pizza
{std::string company;double diameter;double weight;
};int main() {using namespace std;Pizza* pizza = new Pizza;cout << "Enter the diameter of pizza: ";cin >> pizza->diameter;cout << "Enter the weight of pizza: ";cin >> pizza->weight;cin.get();cout << "Enter the pizza company: ";getline(cin, pizza->company);cout << endl<<"Here is the pizza information: "<<endl<< "Company: " << pizza->company << endl<< "Diameter: " << pizza->diameter << endl<< "Weight: " << pizza->weight << endl;delete pizza;return 0;
}

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。

#include <iostream>
#include <string>struct CandyBar
{std::string name;double weight;int calories;
};int main() {using namespace std;CandyBar *p_candybar = new CandyBar [3] {{"Mocha Munch", 2.3, 350},{"Big Rabbit", 5, 300},{"Joy Boy", 4.1, 430}};// 输出第一个结构体元素，按照数组的方式输出cout << "The name of the CandyBar: " << p_candybar[0].name << endl<< "The weight of the candy: " << p_candybar[0].weight << endl<< "The calories information: " << p_candybar[0].calories << endl<<endl;// 输出第二个结构体元素，可以按照指针的逻辑输出cout << "The name of the CandyBar: " << (p_candybar+1)->name << endl<< "The weight of the candy: " << (p_candybar+1)->weight << endl<< "The calories information: " << (p_candybar+1)->calories << endl<<endl;// 输出第三个结构体元素，又是数据的方式cout << "The name of the CandyBar: " << p_candybar[2].name << endl<< "The weight of the candy: " << p_candybar[2].weight << endl<< "The calories information: " << p_candybar[2].calories << endl;delete [] p_candybar;return 0;
}

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（如果编译器不支持 array 类，请使用数组）。

#include <iostream>
#include <array>int main() {using namespace std;array<double, 3> result;cout << "Enter threed result of the 40 meters runing time: \n";cin >> result[0];cin >> result[1];cin >> result[2];double ave_result = (result[0] + result[1] + result[2]) / 3;cout << "The all three time results are: " << result[0] << ", "<< result[1] << ", " << result[2] << endl;cout << "The average result: " << ave_result << endl;return 0;
}

第五章

编写一个要求用户输入两个整数的程序。该程序将计算并输出这两个整数之间（包括这两个整数）所有整数的和。这里假设先输入较小的整数。例如，用户输入的是2和9，则程序将指出2～9之间所有整数的和为44。

#include<iostream>
int main() {using namespace std;int number1, number2;cout << "Enter the first number: ";cin >> number1;cout << "Enter the second number: ";cin >> number2;if (number1 > number2) {int tmp;tmp = number1;number2 = number1;number1 = tmp;}int s = 0;for (int num = number1; num < number2 + 1; ++num)s += num;cout << "Sum the number from " << number1 << " to " << number2<< ", sum = " << s << endl;return 0;
}

使用 array 对象（而不是数组）和 long double（而不是 long long）重新编写程序清单5.4，并计算 100! 的值。

#include<iostream>
#include<array>const int ar_size = 101;
int main() {using namespace std;array<long double, ar_size> factorials;factorials[0] = factorials[1] = 1;for (int i = 2; i < ar_size; ++i) {factorials[i] = factorials[i - 1] * i;}for (int i = 0; i < ar_size ; ++i) {cout << i << "! = " << factorials[i] << endl;}cout << endl;return 0;
}

编写一个要求用户输入数字的程序。每次输入后，程序都将报告到目前为止，所有输入的累计和。当用户输入 0 时，程序结束。

#include<iostream>
int main() {using namespace std;double s =0 ;double ch;while (1) {cout << "Enter a number (int/double) (0 to exit) : ";cin >> ch;if (ch == 0)break;s += ch;cout << "Until now, the sum of the number you inputed is: "<< s << endl;}return 0;
}

Daphne以10%的单利投资了100美元。也就是说，每一年的利润都是投资额的10%，即每年10美元。而Cleo以5%的复利投资了100美元。也就是说，利息是当前存款（包括获得的利息）的5%，Cleo在第一年投资100美元的盈利是5%—得到了105美元。下一年的盈利是105美元的5%—即5.25美元，依此类推。请编写一个程序，计算多少年后，Cleo的投资价值才能超过Daphne的投资价值，并显示此时两个人的投资价值。

#include <iostream>int main() {using namespace std;double daphne_account = 100;double cleo_account = 100;int year = 0;while (cleo_account <= daphne_account) {++year;daphne_account += 10;cleo_account += cleo_account * 0.05;}cout << "After " << year << " Years. " << "Cleo's account is " << cleo_account<< " while more than the one of Daphne which is " << daphne_account << "." << endl;return 0;
}

假设要销售《C++ For Fools》一书。请编写一个程序，输入全年中每个月的销售量（图书数量，而不是销售额）。程序通过循环，使用初始化为月份字符串的 char * 数组（或 string 对象数组）逐月进行提示，并将输入的数据储存在一个int数组中。然后，程序计算数组中各元素的总数，并报告这一年的销售情况。


#include <iostream>
#include <string>int main() {using namespace std;string months[12] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};int sell[12];int total_sales = 0;cout << "Enter the sales of book <<C++ for Fools>> each month." << endl;for (int i=0; i < 12; ++i) {cout << months[i] << ":";cin >> sell[i];total_sales += sell[i];}cout << "\nThe total sales is " << total_sales << endl;for (int i=0; i < 12; ++i) {cout << months[i] << ": " << sell[i] << endl;}return 0;
}

完成编程练习5，但这一次使用一个二维数组来存储输入——3年中每个月的销售量。程序将报告每年销售量以及三年的总销售量。

#include <iostream>
#include <string>int main() {using namespace std;string months[12] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};int sells[3][12];int total_sales[3] = {0, 0, 0};for (int i=0; i<3; ++i) {cout << "Enter " << i+1 << " year(s) sales of book <<C++ for Fools>> each month." << endl;for (int j=0; j<12; ++j) {cout << months[j] << ": ";cin >> sells[i][j];total_sales[i] += sells[i][j];}}for (int i=0; i<3; ++i) {cout << i+1 << " year(s) total sales is " << total_sales[i] << endl;}cout << "There years total sales is " << total_sales[0] + total_sales[1] + total_sales[2] << endl;return 0;
}

设计一个名为 car 的结构体，用它存储下述有关汽车的信息：生产商（存储在字符数组或 string 对象中的字符串）、生产年份（整数）。编写一个程序，向用户询问有多少辆汽车。随后，程序使用new来创建一个由相应数量的 car 结构体组成的动态数组。接下来，程序提示用户输入每辆车的生产商（可能由多个单词组成）和年份信息。请注意，这需要特别小心，因为它将交替读取数值和字符串（参见第4章）。最后，程序将显示每个结构的内容。该程序的运行情况如下:

How many cars do you wish to catalog? 2 Car #1: Please enter the
maker: Hudson Hornet Please enter the year made: 1952 Car #2: Please
enter the maker: Kaiser Please enter the year made: 1951 Here is your
collection: 1952 Hudson Hornet 1951 Kaiser


#include <iostream>
#include <string>int main() {using namespace std;struct Car {string company;int year;  };int car_num = 0;cout << "How many cars do you wish to catalog? ";cin >> car_num;cin.get()  // 读取输入流末尾的回车Car *cars = new Car[car_num];for (int i=0; i < car_num; ++i) {cout << "Please enter the maker: ";cin >> (cars+i)->company;cout << "Please enter the year made: ";cin >> (cars+i)->year;}cout << "\nHere is your collection: \n";for (int i=0; i < car_num; ++i) {cout << cars[i].year << " " << cars[i].company << endl;}delete [] cars;return 0;
}

编写一个程序，它使用一个 char数组和循环，每次读取一个单词，直到用户输入 done 为止。随后，该程序指出用户输入了多少个单词（不包括done在内）。下面是该程序的运行情况：

Enter words (type ‘done’ to stop): anteater birthday category dumpster
envy finagle genometry done for sure

You entered a total of 7 words.

您应在程序中包含头文件 cstring，并使用函数 strcmp() 来进行比较测试。

#include <iostream>
#include <cstring>int main() {using namespace std;int word_count = 0;char ch[80];cout << "Enter a word (type 'done' to stop the program.): \n";do {cin >> ch;if (strcmp(ch, "done") != 0) {word_count++;}} while (strcmp(ch, "done") != 0);cout << "\nYou entered a total of " << word_count << " words." << endl;return 0;
}

编写一个满足前一个练习中描述的程序，但使用 string 对象而不是字符数组。请在程序中包含头文件 string，并使用关系运算符来进行比较测试。

#include <iostream>
#include <string>int main() {using namespace std;int word_count = 0;string ch;cout << "Enter a word (type 'done' to stop the program.): \n";do {cin >> ch;if (ch != "done") {word_count++;}} while (ch != "done");cout << "\nYou entered a total of " << word_count << " words." << endl;return 0;
}

编写一个使用嵌套循环的程序，要求用户输入一个值，指出要显示多少行。然后，程序将显示相应行数的星号，其中第一行包括一个星号，第二行包括两个星号，依此类推。每一行包含的字符数等于用户指定的行数，在星号不够的情况下，在星号前面加上句点。该程序的运行情况如下：

Enter number of rows: 5 Output: …* …** …*** .****


#include <iostream>int main() {using namespace std;int line_num = 0;cout << "Enter the number of rows: ";cin >> line_num;cout << "Output:" << endl;for (int i = line_num; i > 0; --i) {for (int j = i-1; j > 0; --j) {cout << ".";}for (int j = line_num - (i-1); j > 0; --j) {cout << "*";}cout << "\n";}return 0;
}

第六章

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，将小写字符转换为大写（别忘了cctype函数系列）。

#include <iostream>
#include <cctype>int main() {using namespace std;char ch;cout << "Enter any charater: ";while ((ch=cin.get()) != '@') {if (isdigit(ch)) {continue;} else if (islower(ch)) {ch = toupper(ch);} else if (isupper(ch)) {ch = tolower(ch);}cout << ch;}cout << endl<<"That's all!" << endl;return 0;
}

编写一个程序，最多将10个 donation 值读入到一个 double 数组中（如果您愿意，也可使用模板类 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>int main() {using namespace std;const unsigned int size = 10;array<double, size> donation;double sum_value = 0;unsigned int large_avg = 0, n = 0;cout << "Enter 10 double value or type non-digital value to exit: ";while ((n < size) && (cin >> donation[n])) {sum_value += donation[n];++n;}double avg = sum_value / n;for (int i=0; i < n; i++) {if (donation[i]>avg)++large_avg;}cout << "The average value is: " << avg<< ", there are " << large_avg<< " larger than average value." << endl;return 0;
}

编写一个菜单驱动程序的雏形。该程序显示一个提供4个选项的菜单——每个选项用一个字母标记。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一个有效的字母，直到用户这样做为止。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
fPlease enter a c, p, t, or g: q
A maple is a tree.

#include <iostream>int main() {using namespace std;cout << "Please enter one of the following choice: \n";cout << "c) carnivore\tp) pianist.\n"<< "t) tree\tg) game" << endl;bool exit = false;char c;while (!exit && (cin >> c)) {switch (c) {case 'c': cout << "Tiger is a carnivore." << endl;exit = true;break;case 'p':cout << "Mozart is a great pianst." << endl;exit = true;break;case 't':cout << "A maple is a tree." << endl;exit = true;break;case 'g':cout << "Supper Mario is a great game." << endl;exit = true;break;default:cout << "Please enter c, p, t, or g: q" << endl;break;}}return 0;
}

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 strcturestruct bop {char fullname[strsize]; // real namechar title[strsize];    // job titlechar bopname[strsize];  // secret BOP nameint preference;         // 0 = fullname, 1 = title, 2 = bopname
};

该程序创建一个有上述结构体组成的小型数组，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. display by title
c. display by bopname  d. display by preference
q. quit

注意，display by preference 并不意味着显示成员的偏好，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 将显示成员的头衔。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. quitEnter your choices: a
Wimp Macho
Raki Rhodes
Celia Laiter
Hoppy Hipman
Pat HandNext choice： d   
Wimp Macho
Junior Programmer
MIPS
Analyst Trainee
LOOPYNext choice: q
Bye!

#include <iostream>
using namespace std;
const int strsize = 50;
struct bop {char fname[strsize];char title[strsize];char bopname[strsize];int pre;
};
int main() {bop info[5] = {{"Wimp Macho", "W", "Wimp", 0},{"Raki Rhodes", "R", "Raki", 1},{"Celia Laiter", "C", "Celia", 2},{"Hoppy Hipman", "H", "Hoppy", 0},{"Pat Hand", "P", "Pat", 1} };char choice;cout << "benevolent order of progeammers report\n"<< "a)display by name  b)display by title\n"<< "c)display by bopname  d)display by preference\n"<< "q)quit\n";cout << "enter ur choice:";cin >> choice;while (choice != 'q') {switch (choice) {case 'a':for (int i = 0; i < 5; i++)cout << info[i].fname << endl;break;case 'b':for (int i = 0; i < 5; i++)cout << info[i].title << endl;break;case 'c':for (int i = 0; i < 5; i++)cout << info[i].bopname << endl;break;case 'd': {for (int i = 0; i < 5; i++) {switch (info[i].pre) {case 0:cout << info[i].fname << endl;break;case 1:cout << info[i].title << endl;break;case 2:cout << info[i].bopname << endl;break;}}}break;}cout << "next choice:\n";cin >> choice;}cout << "Bye!";return 0;
}

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 + 20000 * 0.15 + 3000 * 0.20，即 4600 tvarps。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>int main() {using namespace std;const double tax_rate1 = 0.1;const double tax_rate2 = 0.15;const double tax_rate3 = 0.20;double income = 0.0, tax = 0.0;cout << "Please enter your income: ";while ((cin >> income) && (income > 0)) {if (income <= 5000) {tax = 0.0;} else if (income <= 15000 ) {tax = (income - 5000) * tax_rate1;} else if (income <= 35000) {tax = (15000 - 5000) * tax_rate1 + (income - 15000) * tax_rate2;} else {tax = (15000 - 5000) * tax_rate1 + (35000 - 15000) * tax_rate2 + (income - 35000) * tax_rate3;}cout << "Income = " << income << ", tax = " << tax << endl;cout << "Please enter your income again or enter a negative value to quit: ";}return 0;
}

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献者数目，然后要求用户输入每一个捐献者的姓名和款项。这些信息被储存在一个动态分配的结构体数组中。每个结构体有两个成员：用来储存姓名的字符数组（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 的捐款者的姓名及其捐款数额。

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 Patrons 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>int main() {using namespace std;const int Grand_Amount = 10000; struct Patron {string name;double amount;};int contribute_num = 0;cout << "Enter the number of contributor: ";cin >> contribute_num;cin.get();  // 读取输入流中的回车符Patron *p_contribution = new Patron [contribute_num];for (int i = 0; i < contribute_num; ++i) {cout << "Enter the name of " << i + 1 << " contributor: ";getline(cin, p_contribution[i].name);cout << "Enter the amount of donation: ";cin >> p_contribution[i].amount;cin.get();  // 读取输入流中的回车符}unsigned int grand_amount_n = 0;cout << "\nGrand patron: " << endl;for (int i = 0; i < contribute_num; ++i) {if (p_contribution[i].amount > Grand_Amount) {cout << "Contributor name: " << p_contribution[i].name << "\n"<< "Contributor amount: " << p_contribution[i].amount << endl;++grand_amount_n;}}if (grand_amount_n == 0) {cout << "None" << endl;}bool is_empty = true;cout << "\nPatrons: " << endl;for (int i=0; i < contribute_num; ++i) {cout << "Contributor name: " << p_contribution[i].name << "\n"<< "Contributor amount: " << p_contribution[i].amount << endl;is_empty = false;}if (is_empty) {cout << "** None **" << endl;}return 0;
}

编写一个程序，它每次读取一个单词，直到用户输入 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符打头的单词，然后对于通过了 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 oxen ambled
quietly across 15 meters of lawn. q5 words beginning with vowels
4 words beginning with consonants
2 others

#include <iostream>
#include <cctype>
#include <string>int main() {using namespace std;unsigned int vowels = 0;unsigned int consonants = 0;unsigned int other = 0;string input;cout << "Enter words (q to quit): " << endl;while (cin >> input) {if (input == "q")break;if (isalpha(input[0])) {switch(toupper(input[0])) {case 'A':;case 'E':;case 'I':;case 'O':;case 'U':++vowels;break;default:++consonants;break;}} else {++other;}}cout << vowels << " words beginning with vowels.\n"<< consonants << " words beginning with consonants.\n"<< other << " words beginning with other letter." << endl;return 0;
}

编写一个程序，它打开一个文件文件，逐个字符地读取该文件，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>int main() {using namespace std;string fn;ifstream in_file_handle;unsigned int n = 0;char ch;cout << "Enter a file name: ";getline(cin, fn);in_file_handle.open(fn.c_str());while ((ch = in_file_handle.get()) != EOF) {++n;}in_file_handle.close();cout << "There are " << n << " characters in " << fn << " file." << endl;return 0;
}

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，余下的内容应为成对的行。在每一对中，第一行为捐款人姓名，第二行为捐款数额。即该文件类似于下面：

4 Sam Stone
2000
Freida Flass
100500
Tammy Tubbs
5000
Rich Raptor
55000

#include <iostream>
#include <fstream>
#include <string>int main() {using namespace std;const int Grand_Amount = 10000;string file_name; ifstream in_file_handle;struct Patron {string name;double amount;};int contribute_num = 0;cout << "Enter a file name: ";getline(cin, file_name);in_file_handle.open(file_name.c_str());in_file_handle >> contribute_num;in_file_handle.get();  // 读取空白Patron *p_contribution = new Patron [contribute_num];for (int i = 0; i < contribute_num; ++i) {/** 4 Sam Stone* 2000* Freida Flass* 100500* Tammy Tubbs* 5000* Rich Raptor* 55000**/getline(in_file_handle, p_contribution[i].name);in_file_handle >> p_contribution[i].amount;in_file_handle.get();   // 读掉空白(包括滞留在行末的回车符)}in_file_handle.close();unsigned int grand_amount_n = 0;cout << "\nGrand patron: " << endl;for (int i = 0; i < contribute_num; ++i) {if (p_contribution[i].amount > Grand_Amount) {cout << "Contributor name: " << p_contribution[i].name << "\n"<< "Contributor amount: " << p_contribution[i].amount << endl;++grand_amount_n;}}if (grand_amount_n == 0) {cout << "None" << endl;}bool is_empty = true;cout << "\nPatrons: " << endl;for (int i=0; i < contribute_num; ++i) {cout << "Contributor name: " << p_contribution[i].name << "\n"<< "Contributor amount: " << p_contribution[i].amount << endl;is_empty = false;}if (is_empty) {cout << "** None **" << endl;}delete [] p_contribution;return 0;
}