day17

Author: bseverac

2020/day17/data.txt

@@ -0,0 +1,8 @@
+#.##....
+.#.#.##.
+###.....
+....##.#
+#....###
+.#.#.#..
+.##...##
+#..#.###

2020/day17/data_test.txt

@@ -0,0 +1,3 @@
+.#.
+..#
+###

2020/day17/main.rb

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+#!/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