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

Problem Statement (Source):

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.

Tip

This question was also solved using the same template in 643. Maximum Average Subarray I.

class Solution {
    public int maxVowels(String s, int k) {
        int start = 0;
        int end = 0;
        int size = s.length();
        String vowels = "aeiou";
        int max = 0;
        int vC = 0; //vowel Count
 
        while(end < size){
            Character ch = s.charAt(end);
            if(vowels.indexOf(ch) != -1){
                vC++;
            }
 
            if(end - start + 1 == k){
                max = Math.max(max, vC);
                if(vowels.indexOf(s.charAt(start)) != -1){
                    vC--;
                }
                start++;
            }
            end++;
        }
 
        return max;
    }
}