[剑指offer 编程题]字符流中第一个不重复的字符

class Solution
{
public:
  //Insert one char from stringstream
    void Insert(char ch)
    {
         s += ch;
    }
  //return the first appearence once char in current stringstream
    char FirstAppearingOnce()
    {
         for(int i=0;i<s.length();i++){
             if(count(s.begin(),s.end(),s[i]) == 1)return s[i];
         }

        return '#';
    }

private:
    string s = "";

};