字符串分割

vector<string> split(const string& s, const string& sep)
{
    vector<string> res;
    string::size_type pos1, pos2;
    pos2 = s.find(sep);
    pos1 = 0;
    while (string::npos != pos2) {
        res.push_back(s.substr(pos1, pos2 - pos1));
        pos1 = pos2 + sep.size();
        pos2 = s.find(sep, pos1);
    }
    if (pos1 != s.length()) {
        res.push_back(s.substr(pos1));
    }
    return res;
}