??????????????????????????
?????????flow.txt?????????????????????м???д?????????
?????????и?????????????????д??
#include<string>
#include<fstream>
#include <iostream>
std::ofstream file;
if (file.bad())
{
std::cout << "cannot open file" << std::endl;;
}
file.open("flow.txt"?? std::ios::app);
file << flow << " ";