Small C++ code : Read & Write file

// reading word by word
ifstream ifile(filename);
vector<string> words
copy(istream_iterator<string>(ifile),
         istream_iterator<string>(),
         back_inserter(words));
ifile.close();

//writing a vector  to file
ofstream outfile;
vector<string> lines;

outfile .open(filename,ofstream::out | ofstream::app);
copy(lines.begin(),
lines.end(),
ostream_iterator<string>(outfile,"\n"));
outfile.close();