AdventOfCode/Days/Day1.cs

using Spectre.Console;

namespace AdventOfCode.Days;

public class Day1 : Day
{
    public override int Number => 1;
    public override string Name => "Historian Hysteria";

    public override void RunPart1(bool display = true)
    {
        List<int> leftNumbers = [];
        List<int> rightNumbers = [];

        foreach (var line in Input.AsSpan().EnumerateLines())
        {
            var separatorIndex = line.IndexOf(' ');

            leftNumbers.Add(int.Parse(line[..separatorIndex]));
            rightNumbers.Add(int.Parse(line[(separatorIndex + 1)..]));
        }

        leftNumbers.Sort();
        rightNumbers.Sort();

        var totalDistance = leftNumbers.Zip(rightNumbers, (a, b) => Math.Abs(a - b)).Sum();

        if (display)
        {
            AnsiConsole.MarkupLine($"[green]Total distance is: [yellow]{totalDistance}[/][/]");
        }
    }

    public override void RunPart2(bool display = true)
    {
        List<int> leftNumbers = [];
        Dictionary<int, int> rightNumbersCount = [];
        var similarityScore = 0;

        foreach (var line in Input.AsSpan().EnumerateLines())
        {
            var separatorIndex = line.IndexOf(' ');

            leftNumbers.Add(int.Parse(line[..separatorIndex]));

            var rightNumber = int.Parse(line[(separatorIndex + 1)..]);

            if (!rightNumbersCount.TryAdd(rightNumber, 1))
            {
                rightNumbersCount[rightNumber]++;
            }
        }

        foreach (var leftNumber in leftNumbers)
        {
            similarityScore += leftNumber * rightNumbersCount.GetValueOrDefault(leftNumber);
        }

        if (display)
        {
            AnsiConsole.MarkupLine($"[green]Similarity score is: [yellow]{similarityScore}[/][/]");
        }
    }
}