1456. Maximum Number of Vowels in a Substring of Given Length

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class Solution:
    def maxVowels(self, s: str, k: int) -> int:
        
        vowels = {"a", "e", "i", "o", "u"}

        count = 0
        for i in range(k):
            if s[i] in vowels:
                count += 1

        maxLength = count

        for i in range(k, len(s)):
            if s[i] in vowels:
                count += 1
            if s[i - k] in vowels:
                count -= 1
            maxLength = max(maxLength, count)

        return maxLength