Day 21 part 1 Ruby solution

Author: creideiki

21-1.rb

@@ -0,0 +1,66 @@
+#!/usr/bin/env ruby
+
+require 'numo/narray'
+
+class Garden
+  attr_accessor :map, :height, :width, :start
+
+  def initialize(input)
+    @height = input.size
+    @width = input[0].size
+    @map = Numo::UInt8.zeros(@width, @height)
+    @start = [-1, -1]
+    @height.times do |y|
+      @width.times do |x|
+        @map[y, x] = 1 if input[y][x] == '#'
+        @start = [y, x] if input[y][x] == 'S'
+      end
+    end
+  end
+
+  def available?(y, x)
+    y >= 0 and y < @height and
+      x >= 0 and x < @width and
+      @map[y, x] == 0
+  end
+
+  def walk(steps)
+    previous_locations = [@start]
+    steps.times do |n|
+      new_locations = []
+      previous_locations.each do |p|
+        new_locations << [p[0] + 1, p[1]] if available?(p[0] + 1, p[1])
+        new_locations << [p[0] - 1, p[1]] if available?(p[0] - 1, p[1])
+        new_locations << [p[0], p[1] + 1] if available?(p[0], p[1] + 1)
+        new_locations << [p[0], p[1] - 1] if available?(p[0], p[1] - 1)
+      end
+      previous_locations = new_locations.uniq
+    end
+    previous_locations.size
+  end
+
+  def inspect
+    to_s
+  end
+
+  def to_s
+    s = "<#{self.class}:\n"
+    @height.times do |y|
+      @width.times do |x|
+        s += case @map[y, x]
+             when 0
+               '.'
+             when 1
+               '#'
+             end
+      end
+      s += "\n"
+    end
+    s += ">"
+  end
+end
+
+input = File.read('21.input').lines.map(&:strip).map(&:chars)
+
+garden = Garden.new(input)
+print garden.walk(64), "\n"