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

Given a string s and an integer k, return the maximum number of vowel letters in any substring of s with length k.

Vowel letters in English are 'a', 'e', 'i', 'o', and 'u'.

Example 1:

Input: s = "abciiidef", k = 3
Output: 3
Explanation: The substring "iii" contains 3 vowel letters.

Example 2:

Input: s = "aeiou", k = 2
Output: 2
Explanation: Any substring of length 2 contains 2 vowels.

Example 3:

Input: s = "leetcode", k = 3
Output: 2
Explanation: "lee", "eet" and "ode" contain 2 vowels.

def maxVowels(self, s: str, k: int) -> int:
	vowels = set('aeiou')
	max_count = count = 0

	# First window
	for i in range(k):
		if s[i] in vowels:
			count += 1
	max_count = count

	# Slide the window
	for i in range(k, len(s)):
		if s[i] in vowels:
			count += 1
		if s[i - k] in vowels:
			count -= 1
		max_count = max(max_count, count)

	return max_count