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.
Example 4:
Input: s = "rhythms", k = 4
Output: 0
Explanation: We can see that s doesn't have any vowel letters.
Example 5:
Input: s = "tryhard", k = 4
Output: 1
Constraints:
1 <= s.length <= 10^5
s consists of lowercase English letters.
1 <= k <= s.length

class Solution:
    def maxVowels(self, s: str, k: int) -> int:
        # version 1: 硬遍历，超时
        res = 0
        vowel = ['a','e','i','o','u']
        for i in range(len(s)-k+1):
            tmp = 0
            tmp_str = s[i:i+k]
            for item in tmp_str:
                if item in vowel:
                    tmp += 1
            res = max(res, tmp)
        return res

class Solution:
    def maxVowels(self, s: str, k: int) -> int:
        # version 2:滑动窗口
        vowel = ['a','e','i','o','u']
        i, j = 0, k
        tmp_str = s[i:j]
        base = 0
        for item in tmp_str:            
            if item in vowel:
                base += 1
        res = base
        for i in range(len(s)-k):
            if s[i] in vowel:
                base -= 1
            if s[i+k] in vowel:
                base += 1
            res = max(res,base)
        return res