题解 | #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) {
      ++counts_[ch];
      s_.push_back(ch);
    }
  //return the first appearence once char in current stringstream
    char FirstAppearingOnce() {
      for (const char& ch : s_)
        if (counts_[ch] == 1)
           return (char) ch;
      
      return '#';
    }
  
private:
  int counts_[128];
  string s_;

};