题解 | #字符流中第一个不重复的字符#

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

哈希表就是好使啊！