Advent of Code - 2025 - Day 5

var input = (await File.ReadAllTextAsync("input.txt")).Split($"{Environment.NewLine}{Environment.NewLine}");

var ranges = input[0].Split(Environment.NewLine).Select(r => {
    var parts = r.Split('-');
    return (Start: long.Parse(parts[0]), End: long.Parse(parts[1]));
}).ToList();
var numbers = input[1].Split(Environment.NewLine).Select(long.Parse);

var part1 = numbers.Count(number => ranges.Any(r => number >= r.Start && number <= r.End));
Console.WriteLine($"Part 1: {part1}");

ranges.Sort((a, b) => a.Start.CompareTo(b.Start));
var concatenatedRanges = new List<(long Start, long End)>();

foreach (var range in ranges)
{
    if (concatenatedRanges.Count == 0 || concatenatedRanges[^1].End < range.Start)
    {
        concatenatedRanges.Add(range);
    }
    else
    {
        var last = concatenatedRanges[^1];
        concatenatedRanges[^1] = (last.Start, Math.Max(last.End, range.End));
    }
}

var part2 = concatenatedRanges.Sum(r => r.End - r.Start + 1);
Console.WriteLine($"Part 2: {part2}");