Longest Palindrome

Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters.

Letters are case sensitive, for example, "Aa" is not considered a palindrome.

class Solution {
    public int longestPalindrome(String s) {
        // Initialize a set to keep track of characters
        Set<Character> charSet = new HashSet<>();
        // Variable to keep track of the length of the palindrome
        int palindromeLength = 0;

        // Iterate over each character in the string
        for(char c : s.toCharArray()) {
            // If the character is already in the set, it means we have a pair
            if(charSet.contains(c)) {
                // Remove the character from the set and increase the palindrome length by 2
                charSet.remove(c);
                palindromeLength += 2;
            } else {
                // If the character is not in the set, add it to the set
                charSet.add(c);
            }
        }

        // If there are any characters left in the set, it means we can add one more character
        // to the center of the palindrome (to make it odd-length)
        if(!charSet.isEmpty()) palindromeLength += 1;

        // Return the length of the longest palindrome that can be built
        return palindromeLength;
    }
}