定长子串中元音的最大数目

/*
 * Problem: Find the maximum number of vowels in a substring of length k in a given string s.
 * Approach: Using Java Streams, we can simplify the iteration and calculation of vowels.
 * We use IntStream to iterate over the possible starting indices of the substrings.
 */

import java.util.Set;
import java.util.HashSet;
import java.util.stream.IntStream;

public class Solution {
    public int maxVowels(String s, int k) {
        // Define the set of vowel characters
        Set<Character> vowels = new HashSet<>(Set.of('a', 'e', 'i', 'o', 'u'));

        // Using IntStream to iterate over the possible starting indices
        return IntStream.rangeClosed(0, s.length() - k)
                .map(i -> (int) s.substring(i, i + k).chars()
                        .filter(c -> vowels.contains((char) c)).count())
                .max().orElse(0);
    }
}