AdventOfCode/AdventOfCode.Solutions/2023/Day 01/Day01.cs

using System.Text.RegularExpressions;

namespace AdventOfCode.Solutions._2023
{
    public class Day01 : IChallange
    {
        public int Year => 2023;
        public int Day => 1;

        private readonly List<string> NumberMapping = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"];
        private readonly InputReader _inputReader;

        public Day01(InputReader inputReader)
        {
            _inputReader = inputReader;
            _inputReader.SetInput(this);
        }

        public async Task<string> GetSolutionPart1()
        {
            int sum = 0;
            await foreach(string line in _inputReader.ReadAsStringLine())
            {
                // get all the numers
                MatchCollection collection = Regex.Matches(line, @"\d");

                // merge first and last index as one
                string values = collection[0].Value + collection[^1].Value;

                // make an int
                sum += int.Parse(values);
            }
            return sum.ToString();
        }

        public async Task<string> GetSolutionPart2()
        {
            int sum = 0;
            await foreach (string line in _inputReader.ReadAsStringLine())
            {
                MatchCollection matchCollection = Regex.Matches(line, @"(\d)");
                List<Match> captures = matchCollection.ToList();

                // replace the text with numbers
                captures.AddRange(Regex.Matches(line, @"(one)"));
                captures.AddRange(Regex.Matches(line, @"(two)"));
                captures.AddRange(Regex.Matches(line, @"(three)"));
                captures.AddRange(Regex.Matches(line, @"(four)"));
                captures.AddRange(Regex.Matches(line, @"(five)"));
                captures.AddRange(Regex.Matches(line, @"(six)"));
                captures.AddRange(Regex.Matches(line, @"(seven)"));
                captures.AddRange(Regex.Matches(line, @"(eight)"));
                captures.AddRange(Regex.Matches(line, @"(nine)"));

                captures = captures.OrderBy(x => x.Index).ToList();

                // merge first and last index as one
                string values = GetStringAsNumber(captures.First().Value) + GetStringAsNumber(captures.Last().Value);
                // make an int
                sum += int.Parse(values);
            }
            return sum.ToString();
        }

        private string GetStringAsNumber(string value)
        {
            return value.Length == 1 ? value : NumberMapping.IndexOf(value).ToString();
        }
    }
}