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

Description

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

 

Solutions

Solution: Sliding Window

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

 

JavaScript

/**
 * @param {string} s
 * @param {number} k
 * @return {number}
 */
const maxVowels = function (s, k) {
  const vowels = new Set(['a', 'e', 'i', 'o', 'u']);
  let left = 0;
  let result = (current = s
    .slice(0, k)
    .split('')
    .filter(char => vowels.has(char)).length);

  for (let index = k; index < s.length; index++) {
    vowels.has(s[index]) && (current += 1);
    vowels.has(s[left]) && (current -= 1);
    left += 1;
    result = Math.max(current, result);
  }
  return result;
};