Day 5 Advent of Code 2020

aoc2020-05.cs

using System;
using System.Collections.Generic;
using System.Linq;
using AdventOfCode.Library;

namespace AdventOfCode
{
    // Day 05 - Massive cleanup
    internal static class Program
    {
        private const bool DoPart1 = true;
        private const bool DoPart2 = true;
        
        public static void Main()
        {
            var data = TextUtility.ReadLines(removeBlank: true);
            var seats = 
                (
                    from s in data
                    let bin = s.Replace('F', '0').Replace('B', '1').Replace('R', '1').Replace('L', '0')
                    select Convert.ToInt32(bin, 2)
                )
               .ToList();
            seats.Sort();
            
            data.Process(DoPart1, 1, seats, Solver1);
            data.Process(DoPart2, 2, seats, Solver2);
        }

        private static string Solver1(List<string> arg1, object arg2)
        {
            var seats = (List<int>) arg2;
            return $"{seats.Max()}";
        }

        private static string Solver2(List<string> arg1, object arg2)
        {
            var seats = (List<int>) arg2;
            long pyramid = seats.Last() * (seats.Last() + 1) / 2 -
                           (seats.First() - 1) * seats.First() / 2;
            long total = seats.Sum();
            
            return $"{pyramid - total}";
        }
    }
}

Took me a while to realize the whole string is just a binary value with dual characters for each 1/0, and there's no need to partition it by seat/row.