using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public class Direction {

        public int Across {get;set;}

        public int Down {get;set;}

    }

    public static void Main()

    {

        var input = @"..##.......

#...#...#..

.#....#..#.

..#.#...#.#

.#...##..#.

..#.##.....

.#.#.#....#

.#........#

#.##...#...

#...##....#

.#..#...#.#";

        var directionsPart1 = new List<Direction>() {

            new Direction { Across = 3, Down = 1},

        };

        var directionsPart2 = new List<Direction>() {

            new Direction { Across = 1, Down = 1},

            new Direction { Across = 3, Down = 1},

            new Direction { Across = 5, Down = 1},

            new Direction { Across = 7, Down = 1},

            new Direction { Across = 1, Down = 2}

        };

        ProcessDirections(input, directionsPart1, "Result for part one: ");

        ProcessDirections(input, directionsPart2, "Result for part two: ");

    }

    public static void ProcessDirections(string input, List<Direction> directions, string label) {                      

        var runningTotal = 1;

        foreach (Direction d in directions) {   

            int i = d.Down;

            var lines = input.Split(new[] { Environment.NewLine }, StringSplitOptions.None);

            var treeCount = 0;

            int position = 0;

            while (i < lines.Length) {

                var line = lines[i];

                string treeLine = line;

​

                position += d.Across;

                while (treeLine.Length < position + 1) {

                    treeLine = $"{treeLine}{line}";

                }

​

                if (treeLine[position] == '#') {

                    treeCount ++;

                }

                i += d.Down;

            }

            runningTotal = runningTotal * treeCount;

        }

        Console.WriteLine($"{label}{runningTotal}");

    }

}