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

Problem

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.

  Constraints:

• 1 <= s.length <= 10^5

• s consists of lowercase English letters.

• 1 <= k <= s.length

Solution (Java)

class Solution {
    private boolean isVowel(char c) {
        return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
    }

    public int maxVowels(String s, int k) {
        int maxVowelCount = 0;
        int vowelCount = 0;

        int i = 0;
        int j = 0;

        while (j < s.length()) {

            char c = s.charAt(j);
            if (isVowel(c)) {
                vowelCount++;
            }

            if ((j - i + 1) == k) {
                maxVowelCount = Math.max(maxVowelCount, vowelCount);
                if (isVowel(s.charAt(i))) {
                    vowelCount--;
                }
                i++;
            }

            j++;
        }

        return maxVowelCount;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).