剑指 Offer 50. 第一个只出现一次的字符
class Solution:
def firstUniqChar(self, s: str) -> str:
if not s:
return " "
dict1 = {}
for i in s:
if i not in dict1:
dict1[i] = 1
else:
dict1[i] += 1
for i,value in dict1.items():
if value == 1:
return i
return " "