Longest Palindrome by Concatenating Two-Letter Words

Statement

Suppose you are given an array of strings, words, and each element in the array has a length of two. You need to return the length of the longest palindrome that can be made by concatenating some elements from words. If no palindrome can be made, return 0.

A palindrome is a sequence of characters that reads the same forward and backward.

Constraints:

• $1 \leq$ words.length $\leq 10^6$
• words[i].length $= 2$
• Each word can be used at most once.

Examples