AdventOfCode/Days/Day5.cs

using Spectre.Console;

namespace AdventOfCode.Days;

public class Day5 : Day
{
    public override int Number => 5;
    public override string Name => "Cafeteria";

    public override void RunPart1(bool display = true)
    {
        var freshIngredients = 0;
        var idRanges = new List<IdRange>();

        var readingRanges = true;
        foreach (var line in Input.EnumerateLines())
        {
            // Read ranges
            if (readingRanges)
            {
                // End of ranges
                if (line.IsWhiteSpace())
                {
                    readingRanges = false;

                    continue;
                }

                var rangeSeparatorIndex = line.IndexOf('-');
                var lower = long.Parse(line[..rangeSeparatorIndex]);
                var upper = long.Parse(line[(rangeSeparatorIndex + 1)..]);

                idRanges.Add(new IdRange(lower, upper));
            }
            else
            {
                // Read ingredients
                var ingredientId = long.Parse(line);
                if (idRanges.Any(range => ingredientId >= range.Lower && ingredientId <= range.Upper))
                {
                    freshIngredients++;
                }
            }
        }

        if (display)
        {
            AnsiConsole.MarkupLine($"[green]Fresh ingredients count: [yellow]{freshIngredients}[/][/]");
        }
    }

    public override void RunPart2(bool display = true)
    {
        var idRanges = new List<IdRange>();
        var rangesToDelete = new List<IdRange>();

        // Read ranges
        foreach (var line in Input.EnumerateLines())
        {
            // End of ranges
            if (line.IsWhiteSpace())
            {
                break;
            }

            var rangeSeparatorIndex = line.IndexOf('-');
            var lower = long.Parse(line[..rangeSeparatorIndex]);
            var upper = long.Parse(line[(rangeSeparatorIndex + 1)..]);

            // Simplify ranges if there is overlap
            rangesToDelete.Clear();
            var skipRange = false;
            foreach (var idRange in idRanges)
            {
                // Distinct
                if (lower > idRange.Upper || upper < idRange.Lower)
                {
                    continue;
                }

                // Outer overlap
                if (lower >= idRange.Lower && upper <= idRange.Upper)
                {
                    skipRange = true;

                    break;
                }

                // Inner overlap
                if (lower <= idRange.Lower && upper >= idRange.Upper)
                {
                    rangesToDelete.Add(idRange);
                }

                // Left overlap
                if (lower >= idRange.Lower && lower <= idRange.Upper)
                {
                    lower = idRange.Lower;

                    rangesToDelete.Add(idRange);
                }

                // Right overlap
                if (upper >= idRange.Lower && upper <= idRange.Upper)
                {
                    upper = idRange.Upper;


                    rangesToDelete.Add(idRange);
                }
            }

            if (!skipRange)
            {
                foreach (var idRange in rangesToDelete)
                {
                    idRanges.Remove(idRange);
                }

                idRanges.Add(new IdRange(lower, upper));
            }
        }

        var freshIngredients = idRanges.Sum(range => (range.Upper - range.Lower) + 1);

        if (display)
        {
            AnsiConsole.MarkupLine($"[green]Fresh ingredients count: [yellow]{freshIngredients}[/][/]");
        }
    }

    private record struct IdRange(long Lower, long Upper);
}