题解 | 字符流中第一个不重复的字符

class Solution
{
private:
    string caseout;
    char candidate;
    //可依据官方题解将记录顺序的vector化为queue，减少需替换candidate时的遍历次数
    //https://blog.nowcoder.net/n/23f5c7b86af64c62b811c2e9ec2cf5b1
    vector<char> MyVec;
    unordered_map<char,int> MyMap;

public:
    Solution(){
        caseout="";
        candidate='#';
    }

  //Insert one char from stringstream
    void Insert(char ch) {
        MyMap[ch]++;
        MyVec.push_back(ch);
        if((candidate!='#'&&ch!=candidate)||(candidate=='#'&&MyMap[ch]!=1)){
            return;
        }
        if(candidate=='#'&&MyMap[ch]==1){
            candidate = ch;
            return;
        }
        if(candidate!='#'&&ch==candidate){
            for(auto VecCh : MyVec){
                if(MyMap[VecCh]==1){
                    candidate = VecCh;
                    return;
                }
            }
            candidate = '#';
            return;
        }
    }
  //return the first appearence once char in current stringstream
    char FirstAppearingOnce() {
        //caseout += candidate;
        //caseout.append(1,candidate);
        return candidate;
    }
};