Advent of Code 2017 Day 1

InverseCaptcha.cs

int InverseCaptchPartOne(string input)
{
	return DoInverseCaptcha(input, _ => 1);
}

int InverseCaptchPartTwo(string input)
{
	return DoInverseCaptcha(input, x => x.Length / 2);
}

int DoInverseCaptcha(string input, Func<int[], int> rotateBy)
{
	var x = input.Cast<char>().Select(c => c - 48).ToArray();

	return x.Zip(x.Skip(rotateBy(x)).Concat(x.Take(rotateBy(x))), (i, j) => i == j ? i : 0).Sum();
}