1456--maximum-number-of-vowels-in-a-substring-of-given-length.md

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

Difficulty: Medium

https://leetcode.com/problems/maximum-number-of-vowels-in-a-substring-of-given-length/

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

My Solution(s):

JavaScript

var maxVowels = function (s, k) {
    let maxVowelsResult = 0;
    const vowels = ['a', 'e', 'i', 'o', 'u'];
    const isVowel = s => s === 'a' || s === 'e' || s === 'i' || s === 'o' || s === 'u';

    // use sliding window
    let left = 0;
    let right = 0;
    let currentVowels = 0;

    while (right < s.length) {
        // if (vowels.includes(s[right])) {
        if (isVowel(s[right])) {
            currentVowels++;
        }
        if (right - left + 1 === k) {
            maxVowelsResult = Math.max(maxVowelsResult, currentVowels);
            // if (vowels.includes(s[left])) {
            if (isVowel(s[left])) {
                currentVowels--;
            }
            left++;
        }
        right++;
    }

    return maxVowelsResult;
};

PHP

class Solution
{
    /**
     * @param String $s
     * @param Integer $k
     * @return Integer
     */
    function maxVowels(string $s, int $k): int {
        $maxVowelsResult = 0;
        $vowels = ['a', 'e', 'i', 'o', 'u'];
        $vowelsCountCurrent = 0;
        $leftIndex = 0;
        $rightIndex = 0;
        $sLength = strlen($s);
        while ($rightIndex < $sLength) {
            if (in_array($s[$rightIndex], $vowels)) {
                $vowelsCountCurrent++;
            }
            if ($rightIndex - $leftIndex + 1 == $k) {
                $maxVowelsResult = max($maxVowelsResult, $vowelsCountCurrent);
                if (in_array($s[$leftIndex], $vowels)) {
                    $vowelsCountCurrent--;
                }
                $leftIndex++;
            }
            $rightIndex++;
        }
        return $maxVowelsResult;
    }
}