Advent Of Code 2020 - Day 3

input.txt

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Program.cs

using System;

namespace adventofcode
{
    class Program
    {
        static void Main()
        {
            var input = System.IO.File.ReadAllLines("input.txt");

            var lineLength = input[0].Length;

            const int right = 3;
            const int down = 1;
            int trees = 0;            
            int positionCounter = 0;

            Console.WriteLine(input[0]);
            for (int i = 1; i < input.Length; i += down)
            {
                var currentLine = input[i];

                var currentLineChars = currentLine.ToCharArray();
                var newPosition = positionCounter += right;
                var currentChar = currentLineChars[newPosition];

                var isTree = currentChar == '#';
                if (isTree) trees++;

                currentLineChars[newPosition] = isTree ? 'X' : 'O';

                Console.WriteLine(currentLineChars);

                if ((positionCounter + right) >= lineLength)
                {
                    positionCounter -= lineLength;
                }
            }

            Console.WriteLine(trees);
        }
    }
}