2131. Longest Palindrome by Concatenating Two Letter Words

https://leetcode.com/problems/longest-palindrome-by-concatenating-two-letter-words/

Python

from collections import Counter


class Solution:
    def longestPalindrome(self, words: List[str]) -> int:
        counts = Counter(words)

        answer = 0
        counted = set()
        is_center_exists = False

        for word, count in counts.items():
            # The word can be used as center
            if word == word[::-1]:
                if count % 2 == 0:
                    answer += count
                else:
                    answer += count - 1
                    is_center_exists = True
                continue

            # Prevent double calculate word already counted ealier
            if word in counted:
                continue


            answer += 2 * min(count, counts[word[::-1]])

            # Mark the reverse word is counted
            counted.add(word[::-1])

        # Every word has length == 2
        answer *= 2

        # Add 2 for center if its exist
        return answer + 2 if is_center_exists else answer