题目描述

blablabla

样例

class Solution:
    res = []
    memo = {}
    def firstAppearingOnce(self):
        """
        :rtype: str
        """
        for ch in self.res:
            if self.memo[ch] == 1:
                return ch
        return "#" 

    def insert(self, char):
        """
        :type char: str
        :rtype: void
        """
        if char not in self.memo:
            self.memo[char] = 1
        else:
            self.memo[char] + 1
        # 这句等效于 
        # self.memo[char] = 1 if char not in self.memo else self.memo[char] + 1 
        # 此处没有+=1 因为else后面是do
        self.res.append(char)