Resolve day 3

3/script.rb

@@ -0,0 +1,98 @@
+#!/usr/bin/env ruby
+
+require_relative '../common'
+
+class Grid
+  def initialize(robosanta: false)
+    @robosanta = robosanta
+
+    @santa_position = Position.new
+    @robosanta_position = Position.new
+
+    @grid = Hash.new(0)
+
+    give_from_santa
+    give_from_robosanta
+  end
+
+  def houses_count
+    @grid.size
+  end
+
+  def move_santa(direction)
+    @santa_position.move direction
+    give_from_santa
+  end
+
+  def move_robosanta(direction)
+    @robosanta_position.move direction
+    give_from_robosanta
+  end
+
+  def give_from_santa
+    @grid[@santa_position.position] += 1
+  end
+
+  def give_from_robosanta
+    return unless @robosanta
+    @grid[@robosanta_position.position] += 1
+  end
+end
+
+class Position
+  attr_accessor :position
+
+  def initialize
+    self.position = [0, 0]
+  end
+
+  def move(direction)
+    case direction
+    when '^'
+      up
+    when 'v'
+      down
+    when '<'
+      left
+    when '>'
+      right
+    end
+  end
+
+  def up
+    self.position = [position[0] - 1, position[1]]
+  end
+
+  def down
+    self.position = [position[0] + 1, position[1]]
+  end
+
+  def left
+    self.position = [position[0], position[1] - 1]
+  end
+
+  def right
+    self.position = [position[0], position[1] + 1]
+  end
+end
+
+def part1
+  Input.new(__dir__).readlines.join.chars.each_with_object(Grid.new) do |direction, grid|
+    grid.move_santa direction
+  end.houses_count
+end
+
+def part2(input)
+  input.chars.each_with_object(Grid.new(robosanta: true)).with_index do |(direction, grid), i|
+    if i.even?
+      grid.move_santa direction
+    else
+      grid.move_robosanta direction
+    end
+  end.houses_count
+end
+
+puts "=== Part 1 ==="
+puts part1
+puts "=== Part 2 ==="
+puts part2(Input.new(__dir__).readlines.join)