# 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

• class Solution {
public int maxVowels(String s, int k) {
int t = 0, n = s.length();
for (int i = 0; i < k; ++i) {
if (isVowel(s.charAt(i))) {
++t;
}
}
int ans = t;
for (int i = k; i < n; ++i) {
if (isVowel(s.charAt(i))) {
++t;
}
if (isVowel(s.charAt(i - k))) {
--t;
}
ans = Math.max(ans, t);
}
return ans;
}

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

• class Solution {
public:
int maxVowels(string s, int k) {
int t = 0, n = s.size();
for (int i = 0; i < k; ++i) t += isVowel(s[i]);
int ans = t;
for (int i = k; i < n; ++i) {
t += isVowel(s[i]);
t -= isVowel(s[i - k]);
ans = max(ans, t);
}
return ans;
}

bool isVowel(char c) {
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
}
};

• class Solution:
def maxVowels(self, s: str, k: int) -> int:
vowels = set('aeiou')
t = sum(c in vowels for c in s[:k])
ans = t
for i in range(k, len(s)):
t += s[i] in vowels
t -= s[i - k] in vowels
ans = max(ans, t)
return ans


• func maxVowels(s string, k int) int {
isVowel := func(c byte) bool {
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u'
}
t := 0
for i := 0; i < k; i++ {
if isVowel(s[i]) {
t++
}
}
ans := t
for i := k; i < len(s); i++ {
if isVowel(s[i]) {
t++
}
if isVowel(s[i-k]) {
t--
}
ans = max(ans, t)
}
return ans
}

• function maxVowels(s: string, k: number): number {
function isVowel(c) {
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
}
let t = 0;
for (let i = 0; i < k; ++i) {
if (isVowel(s.charAt(i))) {
t++;
}
}
let ans = t;
for (let i = k; i < s.length; ++i) {
if (isVowel(s.charAt(i))) {
t++;
}
if (isVowel(s.charAt(i - k))) {
t--;
}
ans = Math.max(ans, t);
}
return ans;
}


• class Solution {
/**
* @param String $s * @param Integer$k
* @return Integer
*/
function isVowel($c) { return$c === 'a' || $c === 'e' ||$c === 'i' || $c === 'o' ||$c === 'u';
}
function maxVowels($s,$k) {
$cnt = 0;$rs = 0;
for ($i = 0;$i < $k;$i++) {
if ($this->isVowel($s[$i])) {$cnt++;
}
}
$rs =$cnt;
for ($j =$k; $j < strlen($s); $j++) { if ($this->isVowel($s[$j - $k])) {$cnt--;
}
if ($this->isVowel($s[$j])) {$cnt++;
}
$rs = max($rs, $cnt); } return$rs;
}
}