determine-if-string-halves-are-alike.java

class Solution {
    // TC : O(len)
    // SC : O(1)
    public boolean halvesAreAlike(String s) {
        Set<Character> vowelSet = new HashSet<>();
        vowelSet.add('a');
        vowelSet.add('e');

        vowelSet.add('i');

        vowelSet.add('o');
        vowelSet.add('u');
        vowelSet.add('A');
        vowelSet.add('E');
        vowelSet.add('I');
        vowelSet.add('O');
        vowelSet.add('U');
        int len = s.length();
        return countVowels(0,len/2,s, vowelSet) == countVowels(len/2,len, s, vowelSet);

    }

    private int countVowels(int startIndex, int endIndex, String s, Set<Character> vowelSet){
        int countV = 0;
        for(int i=startIndex;i<endIndex;i++){
            if(vowelSet.contains(s.charAt(i)))
            {
                countV++;
            }
        }
        return countV;
    }
}