c/c++ 实现split函数

std::vector<std::string> A::split(std::string& str, std::string& flag)
{       std::vector<std::string>   vec;
        size_t   last = 0;
       size_t   index = str.find_first_of(flag,last);
       while(index != std::string::npos)
       {
               vec.push_back(s.substr(last,index-last));
               last = index+1;
                index = s.find_first_of(flag,last);
}
if(index-last>0)
{
vec.push_back(s.substr(last,index-last));
}
return vec;
}