C++, vector를 파일에 저장 질문드립니다

#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <vector>
#include <string.h>
#include <algorithm>
#include <iterator>
using namespace std;
 
class line
{
public:
line(const string& init_string1, const string& init_string2, const string& init_string3);
friend int Compare_By_string1(const line& lhs, const line& rhs);
 
private:
string string1, string2, string3;
};
 
line::line(const string& init_string1, const string& init_string2, const string& init_string3)
:string1(init_string1), string2(init_string2), string3(init_string3){}
 
int Compare_By_string1(const line& lhs, const line& rhs)
{
return (lhs.string1<rhs.string1);
}
 
int main()
{
ifstream file("example.csv");
vector<line> vector_line;
string string1, string2, string3;
 
while(getline(file,string1,',')
&&getline(file,string2,',')
&&getline(file,string3,'\n'))
{
vector_line.push_back(line(string1, string2, string3));
}
file.close();
 
sort(vector_line.begin(), vector_line.end(), Compare_By_string1);
 
/*
ofstream fout("save.csv");
ostream_iterator<vector_line> output_iterator(fout,"\n");
copy(vector_line.begin(), vector_line.end(), output_iterator);
*/
 
return 0;
}