AdventOfCode 2018 Day 02

void Main()
{
    //test if all works
    var testA = new string[] { "abcdef", "bababc", "abbcde", "abcccd", "aabcdd", "abcdee", "ababab", };
    var testB = new string[] { "abcde", "fghij", "klmno", "pqrst", "fguij", "axcye", "wvxyz", };

    //verify
    Debug.Assert(GetAnswerA(testA) == 12);
    Debug.Assert(GetAnswerB(testB) == "fgij");


    //Run
    var aoc = new AdventOfCode(2018, 2);

    //part A
    aoc.SubmitAnswer(GetAnswerA(aoc.InputLines), Part.A);

    //part B
    aoc.SubmitAnswer(GetAnswerB(aoc.InputLines), Part.B);

}

public string GetAnswerB(string[] lines)
{
    string best = "";
    for(int i = 0; i < lines.Length; i++)
    {
        for(int j = i +1; j < lines.Length; j++)
        {
            var score = new string(lines[i].Zip(lines[j], (a,b) => (a, b)) //create tuple to chars
                .Where(x => x.a == x.b) //keep the chars that are identical
                .Select(x=> x.a).ToArray()); //keep 1 of the 2, and create a string

            if(best.Length < score.Length) best = score; //save the longest
        }
    }

    return best;

}

public int GetAnswerA(string[] lines)
{
    return lines.SelectMany(
                            row => row.GroupBy(x => x) //for a string group on chars, and mamre readable tuple
                                    .Select(x => x.Count())
                                    .Where(x => x >= 2) //keep bigger than 2
                                    .Distinct() //remove duplicates
                                )   //we now have for each row, the unique duplicate counts
        .GroupBy(x => x)    //group the counts
        .Select(x => x.Count()) //see how often each is there
        .Aggregate(1, ((x, y) => x * y)) //multiple
        ;
}

// Define other methods and classes here