Longest Palindrome by Concatenating Two Letter Words

두 글자로 된 문자열들을 받고 해당 문자열들을 조합하여

가장 긴 Palindrome 문자열의 길이를 구하는 문제

class Solution {
public:
    int longestPalindrome(vector<string>& words) {
        
        unordered_map<string, int> dataMap{};

        int counter{0};
        string pair{"12"};

        bool selfPalindrome{false};
        int selfPalindromeCounter{0};

        for (int i = 0; i < words.size(); i++)
        {
            selfPalindrome = false;

            pair.front() = words[i].back();
            pair.back() = words[i].front();

            if (words[i].back() == words[i].front())
            {
                selfPalindrome = true;
            }

            if (0 < dataMap[pair])
            {
                if (selfPalindrome)
                {
                    selfPalindromeCounter--;
                }

                dataMap[pair]--;
                counter++;
            }
            else
            {
                if (selfPalindrome)
                {
                    selfPalindromeCounter++;
                }
                dataMap[words[i]]++;
            }
        }

        counter <<= 2;

        if (0 < selfPalindromeCounter)
        {
            counter += 2;
        }

        return counter;
    }
};