题目描述

blablabla

样例

class Solution:
    def firstNotRepeatingChar(self, s):
        """
        :type s: str
        :rtype: str
        """
        if not s:
            return '#'
        memo = {}
        res = []
        for ch in s:
            if ch not in memo:
                memo[ch] = 1
                res.append(ch)
            elif ch in memo:
                memo[ch] += 1
        for ch in res:
            if memo[ch] == 1:
                return ch
        return '#'