从一个字符串中寻找字串

bool find(string s1,string s2)
{
  int pos = 0;
  for(int i = 0,size = s1.size();i < size;i++)
  {
    if(s1[i]==s2[pos])
    {
      pos++;
    }
        if(pos==s1.size())
    return true;
  }
  if(pos == s1.size())
  return true;
  else
  return false;
}