C++primer（第五版）习题答案

前两章习题较简单，这里就不作整理了，直接从第三章开始(持续更新)：

part 1

#include 

using std::cin;
using std::cout;
using std::endl;

int main()
{
    int sum = 0, val = 1;
    while (val <= 10) {
        sum += val;
        ++val;
    }
    cout << "Sum of 1 to 10 inclusive is " << sum << endl;
    return 0;
}

part 2

#include 

using std::cin;
using std::cout;
using std::endl;
using std::cerr;

struct Sales_data   {
    std::string bookNo;
    unsigned unit_sold = 0;
    double revenue = 0.0;
};

int main()
{
    Sales_data data1, data2;
    double price = 0;
    cin >> data1.bookNo >> data1.unit_sold >> price;
    data1.revenue = data1.unit_sold * price;
    cin >> data2.bookNo >> data2.unit_sold >> price;
    data2.revenue = data2.unit_sold * price;
    if (data1.bookNo == data2.bookNo)   {
        unsigned totalCnt = data1.unit_sold + data2.unit_sold;
        double totalRevenue = data1.revenue + data2. revenue;
        cout << data1.bookNo << " " << totalCnt << " " << totalRevenue << " ";
        if (totalCnt != 0)
            cout << totalRevenue/totalCnt << endl;
        else
            cout << "(no sale)" << endl;
        return 0;
    }
    else{
        cerr << "Data must refer to the same ISBN" << endl;
        return -1;
    } 
}

part 1

#include 
#include 

using std::string;
using std::cin;
using std::cout;
using std::endl;

int main()
{
    string line;
    while (getline(cin, line))  {
        cout << line << endl;
    }
    return 0;
}

part 2

#include 
#include 

using std::string;
using std::cin;
using std::cout;
using std::endl;

int main()
{
    string word;
    while (cin >> word)
        cout << word << endl;
    return 0;
}

string类输入运算符(>>)：忽视一切空格，从第一个非空格字符开始，到第一个空格结束；

getline()：包含换行符前的所有空格；

part 1

#include 
#include 

using std::string;
using std::cin;
using std::cout;
using std::endl;

int main()
{
    string st1, st2;
    cin >> st1 >> st2;
    if (st1 == st2)
        cout << "The two strings are equal" << endl;
    else if (st1 > st2)
        cout << "The maximum string is " << st1 << endl;
    else 
        cout << "The maximum string is " << st2 << endl;   
    return 0;
}

part 2

#include 
#include 

using std::string;
using std::cin;
using std::cout;
using std::endl;

int main()
{
    string st1, st2;
    cin >> st1 >> st2;
    if (st1.size() == st2.size())
        cout << "The two strings have the same length " << endl;
    else if (st1.size() > st2.size())
        cout << "The longest string is " << st1 << endl;
    else 
        cout << "The longest string is " << st2 << endl;   
    return 0;
}

part 1

#include 
#include 

using std::string;
using std::cin;
using std::cout;
using std::endl;

int main()
{
    string total_str, str;
    while (cin >> str)
        total_str += str;
    cout << "The concatenated string is " << total_str << endl;
    return 0;
}

part 2

#include 
#include 

using std::string;
using std::cin;
using std::cout;
using std::endl;

int main()
{
    string total_str, str;
    while (cin >> str)
        if (total_str.empty())
            total_str += str;
        else
            total_str += " " +str;
    cout << "The concatenated string is " << total_str << endl;
    return 0;
}