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2237 Longest Palindrome By Concatenating Two Letter Words

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By Anurag
1 min read
2237 Longest Palindrome By Concatenating Two Letter Words

Longest Palindrome by Concatenating Two Letter Words image

You are given an array of strings words. Each element of words consists of two lowercase English letters.

Create the longest possible palindrome by selecting some elements from words and concatenating them in any order. Each element can be selected at most once.

Return the length of the longest palindrome that you can create. If it is impossible to create any palindrome, return 0.

A palindrome is a string that reads the same forward and backward.

 

Example 1:

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**Input:** words = ["lc","cl","gg"]
**Output:** 6
**Explanation:** One longest palindrome is "lc" + "gg" + "cl" = "lcggcl", of length 6.
Note that "clgglc" is another longest palindrome that can be created.

Example 2:

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**Input:** words = ["ab","ty","yt","lc","cl","ab"]
**Output:** 8
**Explanation:** One longest palindrome is "ty" + "lc" + "cl" + "yt" = "tylcclyt", of length 8.
Note that "lcyttycl" is another longest palindrome that can be created.

Example 3:

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**Input:** words = ["cc","ll","xx"]
**Output:** 2
**Explanation:** One longest palindrome is "cc", of length 2.
Note that "ll" is another longest palindrome that can be created, and so is "xx".

 

Constraints:

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1 <= words.length <= 105
words[i].length == 2
words[i] consists of lowercase English letters.

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from collections import Counter

class Solution:
    def longestPalindrome(self, words: List[str]) -> int:
        counter = Counter(words)
        res = 0
        center = 0
        
        for word in list(counter.keys()):
            rev = word[::-1]
            if word != rev:
                pair = min(counter[word], counter[rev])
                res += pair * 4
                counter[word] -= pair
                counter[rev] -= pair
            else:
                pairs = counter[word] // 2
                res += pairs * 4
                counter[word] -= pairs * 2
                if counter[word] == 1:
                    center = 2  # One symmetric word can be in the center
                    
        return res + center
leetcode
python
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