题解 | #字符流中第一个不重复的字符#

class Solution
{
public:
    vector<char> v;
    unordered_map<char, int> hash;
  //Insert one char from stringstream
    void Insert(char ch) {
      v.push_back(ch);
      hash[ch]++;
    }
  //return the first appearence once char in current stringstream
    char FirstAppearingOnce() {
      for (auto &i: v) if (hash[i] == 1) return i;
      return '#';
    }

};