函数备份：按照指定的分隔符，将字符串进行切分

vector < string > Preprocess:: mySplit( string  s, set < string >  stopwords)
{
    vector < string >  wordCollection;
    trim(s, "   " );

     int  nPosBegin = 0 ;
     int  nPosEnd = s.find( ' , ' ,nPosBegin);
     while (nPosEnd != string ::npos)
    {
         string  temp = s.substr(nPosBegin,nPosEnd - nPosBegin);
        trim(temp, "   " );
         if (temp != "" )
        {
            wordCollection.push_back(temp);
        }


        nPosBegin = s.find_first_not_of( ' , ' ,nPosEnd);
         if (nPosBegin == string ::npos)
        {
            nPosEnd = string ::npos;
        }
         else
        {
            nPosEnd = s.find( ' , ' ,nPosBegin);

        }

    }
     if (nPosBegin != string ::npos && nPosEnd == string ::npos) // 结尾缺少分割号，添加该词
    {
         string  temp = s.substr(nPosBegin,s.size() - nPosBegin);
        trim(temp, "   " );
         if (temp != "" )
        {
            wordCollection.push_back(temp);
        }


    }

     return  wordCollection;

}