AdventOfCode/Days/Day1.cs

using Spectre.Console;

namespace AdventOfCode.Days;

public class Day1 : Day
{
    public override int Number => 1;
    public override string Name => "Trebuchet?!";

    private static readonly (string, int)[] WrittenDigits =
    [
        ("one"  , 1),
        ("two"  , 2),
        ("three", 3),
        ("four" , 4),
        ("five" , 5),
        ("six"  , 6),
        ("seven", 7),
        ("eight", 8),
        ("nine" , 9)
    ];

    public override void RunPart1(bool display = true)
    {
        var calibrationSum = 0;

        foreach (var line in Input.AsSpan().EnumerateLines())
        {
            var firstDigitIndex = line.IndexOfAnyInRange('0', '9');
            var lastDigitIndex = line.LastIndexOfAnyInRange('0', '9');

            var firstDigit = line[firstDigitIndex] - '0';
            var lastDigit = line[lastDigitIndex] - '0';

            calibrationSum += firstDigit * 10 + lastDigit;
        }

        if (display)
        {
            AnsiConsole.MarkupLine($"[green]Sum of calibration values is: [yellow]{calibrationSum}[/][/]");
        }
    }

    public override void RunPart2(bool display = true)
    {
        var calibrationSum = 0;

        foreach (var line in Input.AsSpan().EnumerateLines())
        {
            var minFirstDigitIndex = line.IndexOfAnyInRange('0', '9');
            var maxLastDigitIndex = line.LastIndexOfAnyInRange('0', '9');

            var firstDigitValue = 0;
            if (minFirstDigitIndex == -1)
            {
                minFirstDigitIndex = int.MaxValue;
            }
            else
            {
                firstDigitValue = line[minFirstDigitIndex] - '0';
            }

            var lastDigitValue = 0;
            if (maxLastDigitIndex == -1)
            {
                maxLastDigitIndex = int.MinValue;
            }
            else
            {
                lastDigitValue = line[maxLastDigitIndex] - '0';
            }

            foreach (var (writtenDigit, value) in WrittenDigits)
            {
                var firstWrittenDigitIndex = line.IndexOf(writtenDigit);

                if (firstWrittenDigitIndex != -1 && firstWrittenDigitIndex < minFirstDigitIndex)
                {
                    minFirstDigitIndex = firstWrittenDigitIndex;
                    firstDigitValue = value;
                }

                var lastWrittenDigitIndex = line.LastIndexOf(writtenDigit);

                if (lastWrittenDigitIndex != -1 && lastWrittenDigitIndex > maxLastDigitIndex)
                {
                    maxLastDigitIndex = lastWrittenDigitIndex;
                    lastDigitValue = value;
                }
            }

            calibrationSum += 10 * firstDigitValue + lastDigitValue;
        }

        if (display)
        {
            AnsiConsole.MarkupLine($"[green]Sum of calibration values is: [yellow]{calibrationSum}[/][/]");
        }
    }
}