*** Longest Nice Substring (Leetcode 1763)

Tags: Sliding window, Divide and Conquer, Recursion

Problem Link: https://leetcode.com/problems/longest-nice-substring/

class Solution:
    def longestNiceSubstring(self, s: str) -> str:
        
        def fun(string):
            
            n=len(string)
            if(n<2):
                return ""
            s=set(string)
            for i in range(n):
                if(string[i].lower() in s and string[i].upper() in s):
                    continue
                else:
                    l=fun(string[:i])
                    r=fun(string[i+1:])
                    
                    if(len(l)>=len(r)):
                        return l
                    else:
                        return r
            return string
        
        return fun(s)