• 对哈希表、代码的实现能力均需要提高。
class Solution
{
public:
  //Insert one char from stringstream
    map<char,int> m1;
    char cur = ' ';
    int index = 0;
    
    vector<char> res;
    
    void Insert(char ch) {
         m1[ch]++;
         res.push_back(ch);
        
    }
  //return the first appearence once char in current stringstream
    char FirstAppearingOnce() {
      int i = 0;
      if(m1[res[index]] == 1){
          return res[index];
      }else{
          for(i = index; i < res.size(); i++){
              if(m1[res[i]] == 1){
                  index = i;
                  return res[index];
                  
                  
              }
             
          }
          if(i == res.size()){
              index = i - 1;
              return '#';
          }
          else{return res[index];}
      }
    }

};