[C++ Primer] 练习1.23

#include 
#include "Sales_item.h"

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

int main() {
    Sales_item lastItem, currItem;
    int count = 1;
    if (cin >> currItem) {
        lastItem = currItem;
        while (cin >> currItem) {
            if (currItem.isbn() == lastItem.isbn()) {
                ++count;
            } else {
                cout << lastItem.isbn() << " has been sold " << count << " times" << endl;
                count = 1;
            }
            lastItem = currItem;
        }
    }
}