Google Online Assessment 2021 (OA) - Longest Palindrome

A string is a palindrome if it reads the same backward as forwards. For example, "madam" and "racecar" are palindromes, but "milk" is not.

We are given an array of N strings in which each string consist of two lowercase English letters. We would like to join as many strings together as possible in order to obtain a palindrome.


  • arr: an array of length N containing two-letter strings


the length of longest palindrome that can be created by joining as many strings together as possible form arr


Example 1:


1arr = ['ck', 'kc', 'ho', 'kc']

Output: 4


The longest palindrome are "ckkc" and "kcck", and their lengths are both equal to 4.

Try it yourself




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1  >>> a = [1, 2, 3]
2  >>> a[-1]
3  3

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