题解 | #字符流中第一个不重复的字符#

class Solution
{
public:
  //Insert one char from stringstream

    vector<char> res;
    unordered_map<char, int> mp;

    void Insert(char ch) {
         res.push_back(ch);
         mp[ch]++;
    }
  //return the first appearence once char in current stringstream
    char FirstAppearingOnce() {
        for(auto x : res){
            if(mp[x] == 1) return x;
        }
        return '#';
    }

};