[LeetCode][JAVA] 1456. Maximum Number of Vowels in a Substring of Given Length

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

At first, I thought sliding window would be slower than looping two times. Because it should move all the array and looping can choose when to loop. But I got TLE..^-^ So I solved it with the sliding window and it was passed.

class Solution {
    public int maxVowels(String s, int k) {
        int n = s.length();
        char[] chars = s.toCharArray();
        int max = 0;
        String vowels = "aeiou";
        int cnt = 0;

        for (int i = 0; i < k; i++) {
            if (vowels.indexOf(chars[i]) >= 0) cnt++;

        }//for i
        max = Math.max(cnt, max);

        for (int i = k; i < n; i++) {
            if (vowels.indexOf(chars[i-k])>=0) cnt--;
            if (vowels.indexOf(chars[i])>=0) cnt++;

            max = Math.max(cnt, max);
        }
        
        return max;
    }
}