Advent of Code 2020 - Day 3

3.rb

matrix = []
$totaltrees = []
x, y, $trees, slope = 0, 0, 0, -1

File.foreach('3.txt') { |line| matrix << line.strip.split('') and slope += 1 }

possibilities = [[1,1],
                 [3,1],
                 [5,1],
                 [7,1],
                 [1,2]]

possibilities.each do |possibility|
  xtrav = possibility[0]
  ytrav = possibility[1]
    while y < slope
      x += xtrav
      y += ytrav
      if x > 30
        x -= 31
      end
      pos = matrix[y][x]
      if pos == '#'
        $trees += 1
      end
    end
    $totaltrees << $trees
    x, y, $trees = 0, 0, 0
end

puts $totaltrees.reduce(:*)