Advent of Code 2022 - Day 13

using System.Text.Json.Nodes;

var input = await File.ReadAllTextAsync(Path.GetFullPath("..\\..\\..\\..\\..\\inputs\\13.txt"));

var pairs = input.Split("\r\n\r\n");
var pairIndex = 0;
var correctPairs = 0;

foreach (var pair in pairs)
{
    pairIndex++;

    var splitPair = pair.Split("\r\n");
    var left = splitPair[0];
    var right = splitPair[1];
    var jsonLeft = JsonNode.Parse(left);
    var jsonRight = JsonNode.Parse(right);
    var isCorrect = Compare(jsonLeft, jsonRight);
    if (isCorrect == true) correctPairs += pairIndex;
}

Console.WriteLine($"Part 1: {correctPairs}");

var allPackets = input.Split("\r\n").Where(l => !string.IsNullOrEmpty(l)).Select(l => JsonNode.Parse(l)).ToList();
var x = JsonNode.Parse("[[2]]");
var y = JsonNode.Parse("[[6]]");

allPackets.Add(x);
allPackets.Add(y);

allPackets.Sort((left, right) => Compare(left, right) == true ? -1 : 1);

Console.WriteLine($"Part 2: {(allPackets.IndexOf(x) + 1) * (allPackets.IndexOf(y) + 1)}");

bool? Compare(JsonNode left, JsonNode right)
{
    if (left is JsonValue leftVal && right is JsonValue rightVal)
    {
        var leftInt = leftVal.GetValue<int>();
        var rightInt = rightVal.GetValue<int>();
        return leftInt == rightInt ? null : leftInt < rightInt;
    }

    if (left is not JsonArray leftArray) leftArray = new JsonArray(left.GetValue<int>());
    if (right is not JsonArray rightArray) rightArray = new JsonArray(right.GetValue<int>());

    for (var i = 0; i < Math.Min(leftArray.Count, rightArray.Count); i++)
    {
        var res = Compare(leftArray[i], rightArray[i]);
        if (res.HasValue) { return res.Value; }
    }

    if (leftArray.Count < rightArray.Count) { return true; }
    if (leftArray.Count > rightArray.Count) { return false; }

    return null;
}