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 <= 105

• s consists of lowercase English letters.

• 1 <= k <= s.length

Solution

/**
 * @param {string} s
 * @param {number} k
 * @return {number}
 */
var maxVowels = function(s, k) {
    var i = 0;
    var j = 0;
    var count = isVowel(s, j) ? 1 : 0;
    var max = count;
    while (j < s.length - 1) {
        j++;
        count += (isVowel(s, j) ? 1 : 0);
        if (j - i > k - 1) {
            count -= (isVowel(s, i) ? 1 : 0);
            i++;
        }
        max = Math.max(max, count);
    }
    return max;
};

var isVowel = function(s, i) {
    return ['a', 'e', 'i', 'o', 'u'].includes(s[i]);
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(1).