题解 | #字符流中第一个不重复的字符#

class Solution
{
public:
  //Insert one char from stringstream
    void Insert(char ch) {
        counts[ch]++;
        que.push(ch);
        while (!que.empty() && counts[que.front()] > 1) {
            que.pop();
        }
    }
  //return the first appearence once char in current stringstream
    char FirstAppearingOnce() {
        if (que.empty()) {
            return '#';
        }
        return que.front();
    }
private:
    vector<int> counts = vector<int>(128, 0); // 牛客c++版本较低，应该这样初始化
    queue<char> que;
};