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Interactive Lessons
1class Solution:
2 def longestNiceSubstring(self, s: str) -> str:
3 freq = Counter(s)
4 index = 0
5
6 while index < len(s):
7 if not freq[s[index].lower()] or not freq[s[index].upper()]:
8 break
9 index += 1
10
11 # current string is nice
12 if index == len(s):
13 return s
14
15 return max(
16 self.longestNiceSubstring(s[:index]),
17 self.longestNiceSubstring(s[index+1:]),
18 key=len
19 )
20