Year 2016: Day 24

README.md

@@ -8,7 +8,7 @@ I'm also adding notes that may be useful if you're learning Ruby.
 
 Notes for solving:
 * [2015, complete](year_2015.md)
-* [2016, up to day 23](year_2016.md)
+* [2016, up to day 24](year_2016.md)
 * [2023, up to day 04](year_2023.md)
 
 # How to use

spec/year_2016/day_24_input

@@ -0,0 +1,39 @@
+#####################################################################################################################################################################################
+#.....#.#.....#.#.#...#.....#.#.#.#.....#3......#...........#.#.....#.....#.............#.#...#...#.....#...#.........#.#...............#.....#.....#.........................#.....#
+#.#.#.#.#.#.#.#.#.#.#.#.###.#.#.#.#.#.#####.#.#.#.#####.#.###.#.#.###.#.#####.###.#.#.#.#.#####.#.#.#.#####.#.#.#####.#.#.#####.###.#.#.###.###.###.#.###.#.###.###.#.#######.#######
+#.....#...#.#.....#...#.........#...........#.......#...#.#.....#.....#.#.#.......#...#.#...#...#...#.#...#...#.#...#.#.#.#.......#...#...#.....#.....#.....#...#...#.......#.#...#.#
+###.#####.#.#######.###.#.#.#.#.#.#####.#.#.#.#####.#.###.#.#####.#.#.#.#.#####.#.#.#.#.#.###.#.###.#.#####.#.#.#.#.###.#.#.#.###.#.#.#.#.###.#.#.###.#.#.#.#.#.#.#.#.#.#####.#.#.#.#
+#...#1......#.....#.#.#.#.....#.#.#.....#...#.#...#.......#...........#.............#...#.....#.......#.....#.....#.#.......#.#...#.#.#.#.......#...#.#...........#.#.....#...#.#...#
+#.#.###.#.###.#.#.#.#.#.#.#######.#.#.###.#.#.#.###.#####.###.#.#.#.#.#.###.#.#####.#.#.#####.#####.#.#.#.#.#.#.#.###.###.#.#####.#.#.#####.#.#.#.#.#.#.#.###.#####.###.#.#.#.#.###.#
+#.....#.#.....#.#...#.#.....#.#.#.#.........#.#.#.......#.#.#.......#...#...#...#.....#.#...#.......#.....#.......#...#.....#...#...#.......#...#.#.....#...#.#.....#.#...#.#...#...#
+#.#.#.#.#####.#.###.#.#.#.###.#.###.#.#.#####.#.#####.#.#.#.#.#####.#.#.#.###.#######.#.###.#.###.#.#.#.#.#.#.#####.###.#####.#.#.#.#.#####.#####.#.###.#.#.#.#.#.#.#.#####.###.#.###
+#...#.#...#.........#.#...#.#...#.....#.#.....#.......#.........#.....#.....#.........#.....#...#.#.#.#.....#.#.................#.#.#.......#.......#.......#...#...#.......#.#...#.#
+#.#.#.#.#.#.#.###.#.###.###.#.#.#.###.###.#.#.#.#.#.#.#########.#.###.#.#.#####.#.#.#.###.#######.#.###.#.#.#.#.#.#.#.###.#.#.###.#######.#.###.#.#.#.#.###.#.#.#.#####.###.#.#.###.#
+#...#.#.#.#.#...#...#...#.............#.....#.....#...#...#.#.....#...#...#.....#.#.....#...#...........#.#.#.#.......#...#.............#...#.#...#...........#...#2#...#.....#.#.#.#
+###.###.#.#####.#.#.#.#.#.#.#.#.#.#.###.###.#.#.#.###.###.#.#.#.#.#.#.###.###.#.#.#.#.###.#.#.#.###.#####.###.###.#.#.#.###.#######.###.###.#.#.#.#####.#####.###.#.#.#####.#.#.#.###
+#.......#...#...........#.......#...#.#.......#.....#.....#...#...#.#.........#.......#...#.#...#...........#.#...#.#...............#.#.#.....#.......#.#.#.#.....#.........#.#.#.#.#
+###.#.#.#.#.#.#.#####.###.#.#.#.#.#.#.#.#.#.#.#.#.#.#.#####.#.###.#.###.#.#.#.#########.###.#.###.#.###.#.#.#.#.#######.#####.###.#.#.#.#.#####.#####.#.#.#.#.#.#######.#.###.#.#.#.#
+#...#.....#.#.............#...#.#.....#.#...#.......#.........#...#...#.#...#...........#...#...........#...#...#.................#...#.#.#.....#.......#.#.#.......#...#...#...#...#
+###.#.#######.#.#.#.###.#.#.#.###.#.#.#.#.#.###.#####.#.###.#.#.#.###.#.#.#.#.#.#.#.###.#.#.#.#.#.#.#####.#.#####.#.#.#.#.#.#######.#.#.#.###.#.#.#.#.#.###.#.###.#########.###.#.#.#
+#.....#...#.....#.....#...#.........#.#...#.....#...#.................#...#.#.#.......#.....#...#.#.................#.#.#.........#.....#...#.#...#.....#.................#.#.....#.#
+#.#####.#.#.#####.###.#.#.#.###.###.#.#########.#.#######.###.###.#.#.#.#.#.#.#.###.#.#.#####.#.###.#.#########.#.###.###.#.###.###.#.#.#.#.#.###.#####.#.#.#######.#.###.#.#.###.###
+#0#...#.#...#...........#.#.............#.#.......#.....#.#.#.....#.#.#...#.....#.#.#.......#.#...#.................#.#.#.....#...#.#.........#.......#.#...#.......#.......#.....#.#
+#####.#.###.#.#.###.#####.###.#######.###.#.#.###.#.#.#.#.#.#.#.#.###.#.#.#.#.#.#.#.#.#####.###.#.#####.#.#.#.###.#.#.#.#########.#.#.#.###.#.#.###.#.#####.#.#.#.#.#.###.###.#.#.#.#
+#...#.#.....#.#.#...#.......#.#.#...#.........#.......#...#.#.....#.............#...........#...#.#.......#.#.....#.#...........#...#.........#.#...#.#.....#.......#...#.......#...#
+###.###.###.#.###.###.#.###.###.#.#.#.#########.#####.###.#######.#.###.#.#.#.###.#.#.#.#.#.#.#.#####.###.#.#.#.#.#.#.#####.###.#.#.###.#####.#.#.#####.#.#.###.#.#####.#.#.#.#.#.#.#
+#.......#...............#.....#...#...#.#...#.........#...........#.....#.....#.......#...#.....#.......#.#.#.#...#...............#.....#.....#...#.#...#...#.#.#.#.#.....#...#.#.#4#
+#.#.#.#.#.#####.###.#.#####.#.###.#.###.#.#.#.###.###.#.#####.#.#####.#.#######.#.#####.#.#######.#.###.#.#.#.###.###.###.#####.#.###.#.#.#.#####.#.#.#.###.#.#.###.###.#.#.#.#.#.###
+#...#...........#.......#...#.....#.#.......#.....#.........#.#.......#.#...#...#...........#.......#.....#...#...#...#.#...#.....#...#.........#...#...#.....#.....#...#...#...#...#
+###.#.###.#############.#.###.###.#.###.#.#.#.#.#.#.#.#.###.#####.#.#.#.#.#.#####.###.#.#.#.#.###.#.#.#.#.#.###.#.#.###.#.#.#.###.###.#.#.###.#.#.#.#.#.#.#####.#.#.#.#.#.#.###.#.###
+#...#.....#.#...#.#.#.#...........#.......#...#.....#...#...................#...#...#.#.#.#...#.......#...............#...#...#...#...#.#.#5#...#...#.#...#...#.#...#.#...#...#.#...#
+#.###.###.#.#.#.#.#.#.###.#.#######.#.#.#.###.#.#.#.#.#.#.###.#.###.###.#.#.#.#.#.###.#.#.#.#.#.###.#.#.###.#.#.###.#.#.#.#.#.#.#.#.#####.#.#.#######.#.#.#.#.#.#####.#.#######.#.#.#
+#.........#.#...#.#...#...#.............#.....#...#.#.#.#.#.#.....#.#...#.....#.#.#.........#.....#.........#.....#...........#...#.........#.....#...#.#.#.#...#...........#...#...#
+#.#.#.#######.#.#####.#.#.#.###.#.#######.#####.#.#.###.#.#.#.###.###.#.###.#.#.#.###.#.#.#.#####.#.###.#.#.#.#.#.#.#####.#.#.###.#.#.#.#.#####.###.#####.#.#.#.#.###.#.#.#####.#####
+#...#...............#.#.......#.......#.......#.........#.#.#.#...#...#...#.......#.#.....#.#...........#...#.#.#...........#.#...#.......#.........#...#...#.....#...#.#.....#.#...#
+###.#.#.#.#.#########.#.#.#.#.#.#####.#.#######.#.###.#.#.#.###.###.#.#.#.#.#.###.#.#.###.#.#####.#.###########.#.#.#####.#####.#####.#####.#.#.#.#.#.#.#####.#.#.#########.#.###.#.#
+#.#...#.....#.......#.....#...#.......#.#.#...#...#...#.........#...#...#.#...#.#.........#.#.......#.#.#...#...#.........#.#.........#.....#.#.#...#.......#.#.....#.......#.#.....#
+#.#.###.#.###.#.#.#.#.###.#########.#.#.#.#.#.#.###.#.#.#####.#.#.#####.#####.#.#.#########.#.#.#.###.#.#####.#.#.###.###.#.#.#.#.#.#####.###.#.###########.#.#.#.#.#.#######.#####.#
+#........7#.....#.#...#.#.#.#.........#...#.#...........#.....#.......#.........#.........#.....#.......#.#.......#.#.#...#...#.#.#....6#.#.........................#...#.#.......#.#
+#.###.#.###.###.###.#.#.###.###.#####.###.#.#.###.#####.###.#.###.#.#.#.#.#.#.#.#.#####.#.#.#####.#######.#.###.#.#.#####.#####.#.#.#.###.#.#.#.#.#####.#.#.###.#####.#.#.#.#.#.#.#.#
+#.#...#.#...#.#.....#.#.......#...#.....#...#...#...#...#.#.....#...#.#...#...#...#.#.............#.............#.#...#.............#.#.....#.....#.......#.#.#.#.........#...#...#.#
+#####################################################################################################################################################################################

spec/year_2016/day_24_spec.rb

@@ -0,0 +1,33 @@
+require 'year_2016/day_24'
+
+describe Year2016::Day24 do
+  context 'when Part 1' do
+    subject(:sample_one) do
+      <<~HEREDOC
+        ###########
+        #0.1.....2#
+        #.#######.#
+        #4.......3#
+        ###########
+      HEREDOC
+    end
+
+    it 'gives a final result' do
+      expect(described_class.new(sample_one, true).to_i).to eq(14)
+    end
+  end
+
+  context 'when Results' do
+    subject(:input_data) do
+      File.read('spec/year_2016/day_24_input')
+    end
+
+    it 'correctly answers part 1' do
+      expect(described_class.new(input_data, true).to_i).to eq(430)
+    end
+
+    it 'correctly answers part 2' do
+      expect(described_class.new(input_data).to_i).to eq(700)
+    end
+  end
+end

year_2016.md

@@ -334,3 +334,16 @@ Year2016::Day21
 ```
 
 Nothing to say, I'm just a sucker for virtual machines. That said, the test almost takes as long as an episode of Dragon Ball.
+
+## Day 24: Air Duct Spelunking
+
+```
+Year2016::Day24
+  when Part 1
+    gives a final result
+  when Results
+    correctly answers part 1
+    correctly answers part 2
+```
+
+Look here, those are our friends, [BFS](https://en.wikipedia.org/wiki/Breadth-first_search) and [A-*](https://en.wikipedia.org/wiki/A*_search_algorithm)!

year_2016/day_24.rb

@@ -0,0 +1,104 @@
+class Year2016
+  class Day24
+    attr_accessor :max_x, :max_y, :max_num
+
+    # rubocop:disable Metrics/MethodLength
+    def initialize(input_data, input_part_one = false)
+      @version = input_part_one ? 1 : 2
+      @input = input_data.chomp.split("\n")
+      @max_x = @input[0].length
+      @max_y = @input.length
+      @max_num = 0
+      @input = @input.join.chars.map do |char|
+        next true if char == '.'
+        next false if char == '#'
+
+        @max_num = [@max_num, char.to_i].max
+        char.to_i
+      end
+      @distances = {}
+    end
+    # rubocop:enable Metrics/MethodLength
+
+    def safe_passage?(pos_x, pos_y)
+      @input[pos_x + (pos_y * max_x)] != false
+    end
+
+    def position_of(number)
+      idx = @input.index(number)
+      [idx % max_x, (idx / max_x)]
+    end
+
+    EXPAND = [[0, 1], [0, -1], [1, 0], [-1, 0]].freeze
+
+    # rubocop:disable Metrics/AbcSize,  Metrics/CyclomaticComplexity, Metrics/MethodLength, Metrics/PerceivedComplexity
+    def bfs(start, stop)
+      seen = Set.new
+      queue = [[start, 0]]
+      until queue.empty?
+        pos, steps = queue.shift
+        next if seen.include?(pos)
+        return steps if pos == stop
+
+        seen.add(pos)
+        EXPAND.each do |add_x, add_y|
+          next_x = pos[0] + add_x
+          next_y = pos[1] + add_y
+          correct_x = next_x >= 0 && next_x <= max_x
+          correct_y = next_y >= 0 && next_y <= max_y
+          next unless correct_x && correct_y
+          next unless safe_passage?(next_x, next_y)
+
+          queue.push([[next_x, next_y], steps + 1])
+        end
+      end
+      raise 'NOPE'
+    end
+    # rubocop:enable Metrics/AbcSize,  Metrics/CyclomaticComplexity, Metrics/MethodLength, Metrics/PerceivedComplexity
+
+    def numbers
+      @numbers ||= (0..max_num).to_a
+    end
+
+    # rubocop:disable Metrics/CyclomaticComplexity, Metrics/MethodLength
+    def shortest_path(pos, done, todo, path, best_path)
+      return if path > best_path
+      return path + distance(pos, 0) if todo.empty? && @version == 2
+      return path if todo.empty? && @version == 1
+
+      todo.each do |next_pos|
+        next_done = done + [next_pos]
+        next_todo = todo - [next_pos]
+        next_dist = distance(pos, next_pos)
+        next_path = shortest_path(next_pos, next_done, next_todo, path + next_dist, best_path)
+        best_path = [best_path, next_path].min if next_path
+      end
+      best_path
+    end
+    # rubocop:enable Metrics/CyclomaticComplexity, Metrics/MethodLength
+
+    def distance(from, to)
+      @distances[[from, to].sort]
+    end
+
+    def calculate_distances
+      numbers.combination(2) do |combo|
+        combo.sort!
+        dist = bfs(position_of(combo[0]), position_of(combo[1]))
+        @distances[combo] = dist
+      end
+    end
+
+    def to_i
+      calculate_distances
+      best_path = 1000
+      numbers[1..].each do |next_pos|
+        next_done = [0, next_pos]
+        next_todo = numbers - next_done
+        next_path = shortest_path(next_pos, next_done, next_todo, distance(0, next_pos), best_path)
+        best_path = [best_path, next_path].min if next_path
+      end
+      best_path
+    end
+  end
+end