How to Solve Longest Nice Substring Problem
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Longest Nice Substring
A string s is nice if, for every letter of the alphabet that s contains, it appears both in uppercase and lowercase. For example, "abABB" is nice because 'A' and 'a' appear, and 'B' and 'b' appear. However, "abA" is not because 'b' appears, but 'B' does not. Given a string s, return the longest substring of s that is nice. If there are multiple, return the substring of the earliest occurrence. If there are none, return an empty string.
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Understanding the Longest Nice Substring Problem
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Problem Statement
A string s is nice if, for every letter of the alphabet that s contains, it appears both in uppercase and lowercase. For example, "abABB" is nice because 'A' and 'a' appear, and 'B' and 'b' appear. However, "abA" is not because 'b' appears, but 'B' does not. Given a string s, return the longest substring of s that is nice. If there are multiple, return the substring of the earliest occurrence. If there are none, return an empty string.
Longest Nice Substring
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Examples
# Example 1
s = "YazaAay"
"aAa"
# Example 2
s = "Bb"
"Bb"
# Example 3
s = "c"
""
Constraints
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Solve Longest Nice Substring — A string s is nice if, for every letter of the alphabet that s contains, it appe...
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Time: O(n) | Space: O(n)
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