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 = 3Output: 3Explanation: The substring "iii" contains 3 vowel letters.

Example 2:

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

Example 3:

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

?

Constraints:

• 1 <= s.length <= 105

• s?consists of lowercase English letters.

• 1 <= k <= s.length

1：寫一個方法，判斷是否是元音字母；

2：設(shè)置一個前綴和的數(shù)組；

3：依次判斷連續(xù)K個數(shù)字之和，保存最大值；

4：返回最大值；

Runtime:?7 ms, faster than?99.58%?of?Java?online submissions for?Maximum Number of Vowels in a Substring of Given Length.

Memory Usage:?43.2 MB, less than?31.48%?of?Java?online submissions for?Maximum Number of Vowels in a Substring of Given Length.