c++primerplus(第六版)编程题——第5章（循环和关系表达式）

声明：作者为了调试方便，每一章的程序写在一个工程文件中，每一道编程练习题新建一个独立文件，在主函数中调用,我建议同我一样的初学者可以采用这种方式，调试起来会比较方便。

(具体方式参见第3章模板)

1. 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。

#include <iostream>
using namespace std;

void cprimerplus_exercise_5_1()
{
    cout << "Please input two integers!" <<endl;
    int a , b, c;
    int sum = 0;
    cout << "Please input the smaller one:";
    cin >> a;
    c = a;
    cout <<"Please input the larger one:";
    cin >> b;
    for ( a; a <= b; a++)
    {
        sum += a;
    }

    cout << "The sum of numbers between " << c << " and " << b << " is "<< sum << endl;

}

2.使用array对象（不是数组）和long double（不是long long）重新编写程序清单5.4，并计算100！的值。（编译器不支持array）

#include <iostream>
#include <array>
using namespace std;
const int ArSize = 100;
void cprimerplus_exercise_5_2() //have a problem
{
    array<long double, 100>arr;
    arr[1] = arr[0] = 1;
    
    for( int i = 2; i <= ArSize; i++)
        arr[i] = i * arr[i-1];
    
    for (int i = 0; i <= ArSize; i++)
    {
        cout << i << " != "<< arr[i] << endl;
    }
}

3.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，所有输入的累积和。当用户输入0是结束程序。

#include <iostream>
using namespace std;

void cprimerplus_exercise_5_3()
{
    
    int a = 0;
    cout << "Please input a number:";
    cin >> a;
    int sum = 0;
    int cnt = 0;

    while (a != '\0')
    {
        sum += a;
        ++ cnt;    
        cout << "utile now, the total sum of "<< cnt <<" numbers is " << sum << endl;
        
        cout << "Please input a number:";
        cin >> a;
    }
    
}

4. 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100美元，也就是说，利息是当前存款（包括获得的利息）的5%；请编写一个程序，计算多少年以后，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>
using namespace std;
const double simplerate = 0.1;
const double compoundrate = 0.05;
const int principal = 100;
void cprimerplus_exercise_5_4()
{
    double sum1 = principal;
    double sum2 = 0.0;
    int year = 0;
    while (sum2 < sum1)
    {
        ++year;
        sum1 +=10;
        sum2 = (principal + sum2) * compoundrate + sum2;

    }

    cout << "After" << year << "years, Cleo's investment income can surpass Daphne!" <<endl;
    cout << "At the time, Cleo's income is "<< sum2 << " , while Daphne's income is " << sum1 << endl;
    //system("pause");
}

5. 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int数组中。然后，程序计算数组中个元素的总数，并报告这一年的销售情况。

#include <iostream>
using namespace std;
void cprimerplus_exercise_5_5()
{
    const char* months[12] = { "January", "February", "March", "April",\
        "May", "June", "July", "August",\
        "September", "October", "November", "December"};

    int salesnumber[12], sum = 0;
    for (int i = 0; i < 12; i++)
    {
        cout << "Please input the " << *(months + i) << " sales numbers:"<< endl;
        cin >> salesnumber[i];
        cin.get();
        sum += salesnumber[i];
    }

    cout << "The total sales number of this year is " << sum << endl;
}

6.完成编程练习5，当这一次使用一个二维数组来储存输入——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>
using namespace std;
void cprimerplus_exercise_5_6()
{
    const char* months[12] = { "January", "February", "March", "April",\
        "May", "June", "July", "August",\
        "September", "October", "November", "December"};
    const char* years[3] = { "First year", "Second year", "Third year"};

    int salesnumber[3][12], sum = 0, tmp =0, year_sale[3];
    for (int i = 0; i < 3; i++)
    {
        cout << "Please input the " << *(years + i) << " years every month's numbers:"<< endl;
        for (int j = 0; j < 12; j++)
        {
            cout << *( months + j) << " sales number is :";
            cin >> salesnumber[i][j];
            cin.get();
            tmp += salesnumber[i][j];
        }
        year_sale[i] = tmp;
        tmp = 0;

        sum += year_sale[i];

    }
    for (int i = 0; i < 3; i++)
    {
        cout << *(years + i) << "year sales number is " << year_sale[i] <<endl;
    }
    cout << "The total sales number of this year is " << sum << endl;
}

7.设计一个名为car的结构，用它储存下述有关汽车的信息；生产商（储存在字符数组或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来创建一个有相应数量的car结构组成的动态数组。接下来，程序提示用户输入每辆车的生产商（可能有多个单词组成）和年份信息。请注意：这需特别小心，因为它将交替读取数值和字符串。最后，程序将显示每个结构的内容。

#include <iostream>
#include <string>

using namespace std;

void cprimerplus_exercise_5_7()
{
    struct car
    {
        string carmaker;
        //char carmaker[20];
        int makeyear;
    };

    cout << "How many cars do you wish to catalog?";
    int num;
    cin >> num;
    cin.get();
    
    car *cars = new car[num];
    
    for (int i = 0; i < num; i++)
    {
        cout << "Car #" << i+1 << ":"<< endl;
        
        cout << "Please enter the maker:";
        //cin >> cars[i].carmaker;
        getline(cin, cars[i].carmaker);

        cout << "Please enter the year made:" ;
        cin >> cars[i].makeyear;
        cin.get();
    }

    cout << "Here is your collection:" << endl;
    for (int i = 0; i< num; i++)
    {        
        cout << cars[i].makeyear << '\t' << cars[i].carmaker << endl;
    }
}

8.编写一个程序，它使用一个char数组和循环来每次读取一个单词，直到用户输入done为止。随后，该程序指出用户输入多少个单词（不包括done在内）。你应在程序中包含头文件cstring.h，并使用函数strcmp()来进行比较测试。

#include <iostream>
#include <cstring>

using namespace std;

void cprimerplus_exercise_5_8()
{
    cout << "Enter words (to stop, type the word 'done'):"<<endl;
    char words[20];
    cin >> words;
    int cnt = 0;
    
    while (strcmp(words,"done") != 0)
    {
        ++cnt;
        cin >> words;

    }

    cout << "you entered a total of " << cnt << " words." << endl;
}

9.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>

using namespace std;

void cprimerplus_exercise_5_9()
{
    cout << "Enter words (to stop, type the word 'done'):"<<endl;
    string words;
    cin >> words;
    
    int cnt = 0;

    while (words != "done")
    {
        ++cnt;
        cin >> words;

    }

    cout << "you entered a total of " << cnt << " words." << endl;
}

10.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，以此类推。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，在星号前面加上句号。

#include <iostream>

using namespace std;

void cprimerplus_exercise_5_10()
{
    cout << "Enter number of rows:";
    int rows; 
    cin >> rows;
    cin.get();
    for (int i = 1; i <= rows; i++)
    {
        for( int j = 0; j < rows - i; j++)
        {
            cout << ".";
        }
        for (int k = 0; k < i; k++)
        {
            cout << "*";
        }
        cout << endl;

    }
    
}