void split(const string& str, vector<string>& ret_, string sep)--传入要分割的字符串str，要存储分割字符串的ret，分割的字符串str
{
if (str.empty())
{
return;
}
string tmp;
string::size_type pos_begin = str.find_first_not_of(sep);
string::size_type comma_pos = 0;
while (pos_begin != string::npos)
{
comma_pos = str.find(sep, pos_begin);
if (comma_pos != string::npos)
{
tmp = str.substr(pos_begin, comma_pos - pos_begin);
pos_begin = comma_pos + sep.length();
}
else
{
tmp = str.substr(pos_begin);
pos_begin = comma_pos;
}
if (!tmp.empty())
{
ret_.push_back(tmp);
tmp.clear();
}
}
}