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)
    {
        str += ch;
        count[ch]++;
    }
  //return the first appearence once char in current stringstream
    char FirstAppearingOnce()
    {
        for(int i = 0;i<str.size();i++){
            if(count[str[i]] == 1)
                return str[i];
        }
        
        return ‘#‘;
    }

private:
    int count[256]={0};
    string str;
};