《C++ Primer》第五版课后习题解答_第三章（1）(01-05)

系统环境： windows 10 1703

编译环境：Visual studio 2017

3.1

//1.9#include <iostream>using std::cout;using std::endl;int main(){    int sum = 0, i = 50;    while (i <= 100)    {        sum += i;        ++i;    }    cout << "The sum is: " << sum << endl;    return 0;}

//1.10#include <iostream>using std::cout;using std::endl;int main(){    int i = 10;    while (i >= 0)    {        cout << i << endl;        --i;    }    return 0;}

//1.11#include <iostream>using std::cout;using std::endl;using std::cin;int main(){    cout << "Enter two integers:" << "\n" << endl;    int i1 = 0, i2 = 0;    cin >> i1 >> i2;    if (i1 >= i2)    {        i1 = i1 + i2;        i2 = i1 - i2;        i1 = i1 - i2;    }    cout << "\n" << endl;    for (int i = i1; i <= i2; ++i)    {        cout << i << endl;    }    return 0;}

//综合1.5.1节，1.5.2节，1.6节程序如下#include <iostream>#include <string>using std::cout;using std::endl;using std::cin;using std::string;//创建 Sales_data 类struct Sales_data {    string bookID;    unsigned sum_sold = 0;    float price = 0.0;    float revenue = 0.0;};int main(){    cout << "Enter sales record:" << "\n" << endl;    Sales_data trans, book;    int cnt = 1;    if (cin >> book.bookID >> book.sum_sold >> book.price) //读取第一个数据    {        book.revenue = book.sum_sold * book.price;        while (cin >> trans.bookID >> trans.sum_sold >> trans.price) //读取剩余的数据        {            trans.revenue = trans.sum_sold * trans.price;            if (trans.bookID == book.bookID) //判断读入的 bookID 是否和第一个数据的 bookID 相同            {                book.revenue += trans.revenue;                book.sum_sold += trans.sum_sold;                ++cnt;            }            else            {                cout << cnt << " " << book.bookID << " " << book.sum_sold << " " << book.revenue << endl;                book.bookID = trans.bookID;                book.sum_sold = trans.sum_sold;                book.revenue = trans.revenue;                cnt = 1;            }        }        cout << cnt << " " << book.bookID << " " << book.sum_sold << " " << book.revenue << endl;    }    return 0;}

3.2

#include <iostream>#include <string>using std::cout;using std::endl;using std::cin;using std::string;//读入一整行int main(){    string s;    while (getline(cin, s))        cout << s << endl;    return 0;}

#include <iostream>#include <string>using std::cout;using std::endl;using std::cin;using std::string;//一次读入一个词int main(){    string s;    while (cin >> s)        cout << s << endl;    return 0;}

3.3

string 类的输入运算符，自动忽略开头的空白，并从第一个真正的字符还是读取，直到遇见下一处空白开始；

getline 会读取一行中的所有内容，直到遇到一个换行符为止（换行符也被读入了）。

3.4

#include <iostream>#include <string>using std::cout;using std::endl;using std::cin;using std::string;//比大小int main(){    string s1, s2;    cout << "Enter two strings:" << endl;    cin >> s1 >> s2;    if (s1 == s2)    {        cout << "Two strings are equal" << endl;    }    else    {        if (s1 > s2)        {            cout << s1 << endl;        }        else        {            cout << s2 << endl;        }    }    return 0;}

#include <iostream>#include <string>using std::cout;using std::endl;using std::cin;using std::string;//比长度int main(){    string s1, s2;    cout << "Enter two strings:" << endl;    cin >> s1 >> s2;    if (s1.size() == s2.size())    {        cout << "Two strings are isometric" << endl;    }    else    {        if (s1.size() > s2.size())        {            cout << s1 << endl;        }        else        {            cout << s2 << endl;        }    }    return 0;}

3.5

#include <iostream>#include <string>using std::cout;using std::endl;using std::cin;using std::string;//直接连接int main(){    string sum, s;    while (cin >> s)    {        sum += s;    }    cout << sum << endl;    return 0;}

#include <iostream>#include <string>using std::cout;using std::endl;using std::cin;using std::string;//用空格连接int main(){    string sum, s;    while (cin >> s)    {        sum += s;        sum += " ";    }    cout << sum << endl;    return 0;}