[C++ Primer] 练习2.41

#include <iostream>

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

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

int main() {
    Sales_data book1, book2;
    cin >> book1.bookNo >> book1.book_sold >> book1.revenue;
    cin >> book2.bookNo >> book2.book_sold >> book2.revenue;

    if (book1.bookNo == book2.bookNo) {
        cout << book1.bookNo
             << " sold: "
             << book1.book_sold + book2.book_sold
             << ", revenue: "
             << (book1.book_sold * book1.revenue + book2.book_sold * book2.revenue) /
                (book1.book_sold + book2.book_sold)
             << endl;
    } else {
        cout << "book isbn number not match!" << endl;
    }

    return 0;
}