题解 | #字符流中第一个不重复的字符#

set存放当前已经存在的字符

chs存发当前唯一存在的字符队列

unique这个唯一的字符

import java.util.*;

public class Solution {
    Set<Character> set = new HashSet<>();
    LinkedList<Character> chs = new LinkedList<>();//当前唯一的字符
    char unique = '#';
    public void Insert(char ch)
    {
        if(set.contains(ch)){
            chs.remove(new Character(ch));//删
            if(ch == unique){
                if(chs.size() == 0)unique = '#';
                else unique = chs.getFirst();
            }
        } else {
            if(unique == '#')unique = ch;
            chs.add(ch);
        }
        set.add(ch);
    }
  //return the first appearence once char in current stringstream
    public char FirstAppearingOnce()
    {
        return unique;
    }
}