409. Longest Palindrome

Python

class Solution:
    def longestPalindrome(self, s: str) -> int:
        s_set = set(list(s))
        count = 0
        count_solo = False
        for ch in s_set:
            ch_count = s.count(ch) // 2
            count += ch_count * 2
            if s.count(ch) % 2 != 0:
                count_solo = True
        
        if count_solo:
            count += 1
        return count