day17

bseverac · bseverac · commit f3dbff68a9b7 · 2020-12-17T22:12:08.000+01:00
diff --git a/2020/day17/data.txt b/2020/day17/data.txt
@@ -0,0 +1,8 @@
+#.##....
+.#.#.##.
+###.....
+....##.#
+#....###
+.#.#.#..
+.##...##
+#..#.###
diff --git a/2020/day17/data_test.txt b/2020/day17/data_test.txt
@@ -0,0 +1,3 @@
+.#.
+..#
+###
diff --git a/2020/day17/main.rb b/2020/day17/main.rb
@@ -0,0 +1,75 @@
+#!/usr/bin/ruby
+require 'matrix'
+require 'test/unit'
+require 'pry'
+
+class Day17
+  attr_accessor :cells
+
+  def initialize(grid, d)
+    @d = d
+    @cells = {}
+    grid.split("\n").each.with_index { |line, y|
+      line.split(//).each.with_index.select{ |c, _| c == '#'}.each  { |_, x|
+        self.add_cell(([0] * @d).zip([x, y]).map(&:compact).map(&:sum))
+      }
+    }
+  end
+
+  def step
+    @cells = cells_to_evaluate.each_with_object({}) do |c, cells|
+      cells[c] = true if activated?(c)
+    end
+  end
+
+  def activated?(c)
+    (@cells[c] && (2..3).include?(closed_active(c))) ||
+    (!@cells[c] && closed_active(c) == 3)
+  end
+
+  def cells_to_evaluate
+    @cells.map { |c, _| closed_cells(c) + [c] }.flatten(1).uniq
+  end
+
+  def add_cell(c)
+    @cells[c] = true
+  end
+
+  def closed_cells(c)
+    [1, 0, -1].repeated_permutation(@d).reject { |c| c == [0] * @d }.map{ |ac|
+      c.zip(ac).map(&:sum)
+    }
+  end
+
+  def closed_active(c)
+    closed_cells(c).count { |c| @cells[c] }
+  end
+end
+
+#start 20:40
+#end   22:10
+class Day17Test < Test::Unit::TestCase
+  def test_star_1
+    solver = Day17.new(File.read('data_test.txt'), 3)
+    6.times { |_| solver.step }
+    assert_equal 112, solver.cells.count
+  end
+
+  def test_star_1_final
+    solver = Day17.new(File.read('data.txt'), 3)
+    6.times { |_| solver.step }
+    assert_equal 230, solver.cells.count
+  end
+
+  def test_star_2
+    solver = Day17.new(File.read('data_test.txt'), 4)
+    6.times { |_| solver.step }
+    assert_equal 848, solver.cells.count
+  end
+
+  def test_star_2_final
+    solver = Day17.new(File.read('data.txt'), 4)
+    6.times { |_| solver.step }
+    assert_equal 1600, solver.cells.count
+  end
+end
