AdventOfCode2025/AdventOfCode2025/Solutions/Day5.cs

using AdventOfCode2025.Inputs;

namespace AdventOfCode2025.Solutions;

public class Day5() : Solution(5)
{
    public override string SolvePart1()
    {
        List<string> lines = Input.Lines.ToList();
        List<Range> freshRanges = GetFreshRanges(lines);
        int freshIngredients = lines[(freshRanges.Count + 1)..].Select(long.Parse).Count(id => IsFresh(id, freshRanges));
        return freshIngredients.ToString();
    }

    public override string SolvePart2()
    {
        List<string> lines = Input.Lines.ToList();
        List<Range> ranges = GetFreshRanges(lines).OrderBy(x => x.From).ThenBy(x => x.To).ToList();

        var merged = new List<Range>();
        Range current = ranges[0];

        for (var i = 1; i < ranges.Count; i++)
        {
            Range next = ranges[i];

            if (next.From <= current.To)
            {
                current.To = Math.Max(current.To, next.To);
            }
            else
            {
                merged.Add(current);
                current = next;
            }
        }

        merged.Add(current);

        return merged.Sum(r => r.To - r.From + 1).ToString();
    }

    private static List<Range> GetFreshRanges(List<string> lines) => lines
        .TakeWhile(line => !string.IsNullOrEmpty(line))
        .Select(range => range.Split('-').Select(long.Parse).ToArray())
        .Select(v => new Range(v))
        .ToList();

    private static bool IsFresh(long id, IEnumerable<Range> ranges) => ranges.Any(range => IsFresh(id, range));

    private static bool IsFresh(long id, Range range) => id >= range.From && id <= range.To;

    private sealed class Range(long[] values)
    {
        public long From { get; } = values[0];
        public long To { get; set; } = values[1];
    }
}