Year 2015: Day 14

README.md

@@ -7,7 +7,7 @@ Consistency is hard without proper goals to set a good (let's dare say "atomic")
 I'm also adding notes that may be useful if you're learning Ruby.
 
 Notes for solving:
-* [2015, up to day 13](year_2015.md)
+* [2015, up to day 14](year_2015.md)
 * [2023, up to day 03](year_2023.md)
 
 # How to use

spec/year_2015/day_14_input

@@ -0,0 +1,9 @@
+Vixen can fly 8 km/s for 8 seconds, but then must rest for 53 seconds.
+Blitzen can fly 13 km/s for 4 seconds, but then must rest for 49 seconds.
+Rudolph can fly 20 km/s for 7 seconds, but then must rest for 132 seconds.
+Cupid can fly 12 km/s for 4 seconds, but then must rest for 43 seconds.
+Donner can fly 9 km/s for 5 seconds, but then must rest for 38 seconds.
+Dasher can fly 10 km/s for 4 seconds, but then must rest for 37 seconds.
+Comet can fly 3 km/s for 37 seconds, but then must rest for 76 seconds.
+Prancer can fly 9 km/s for 12 seconds, but then must rest for 97 seconds.
+Dancer can fly 37 km/s for 1 seconds, but then must rest for 36 seconds.

spec/year_2015/day_14_sample_one

@@ -0,0 +1,2 @@
+Comet can fly 14 km/s for 10 seconds, but then must rest for 127 seconds.
+Dancer can fly 16 km/s for 11 seconds, but then must rest for 162 seconds.

spec/year_2015/day_14_spec.rb

@@ -0,0 +1,37 @@
+require 'year_2015/day_14'
+
+describe Year2015::Day14 do
+  context 'when Part 1' do
+    subject(:sample_one) do
+      described_class.new(File.read('spec/year_2015/day_14_sample_one'), true)
+    end
+
+    it 'gives a final result' do
+      expect(sample_one.to_i(1000)).to eq(1120)
+    end
+  end
+
+  context 'when Part 2' do
+    subject(:sample_one) do
+      described_class.new(File.read('spec/year_2015/day_14_sample_one'))
+    end
+
+    it 'gives a final result' do
+      expect(sample_one.to_i(1000)).to eq(689)
+    end
+  end
+
+  context 'when Results' do
+    subject(:input_data) do
+      File.read('spec/year_2015/day_14_input')
+    end
+
+    it 'correctly answers part 1' do
+      expect(described_class.new(input_data, true).to_i(2503)).to eq(2655)
+    end
+
+    it 'correctly answers part 2' do
+      expect(described_class.new(input_data).to_i(2503)).to eq(1059)
+    end
+  end
+end

year_2015.md

@@ -230,3 +230,18 @@ Year2015::Day13
 Again, refer to [Day 09][##day-09] because we are in a similar configuration, with the exception that we must rejoin our starting point at the end. Nothing too complicated.
 
 Second part is just adding another node with a 0 relationship to all nodes. Surprisingly, it seems our presence lowered the general happiness...
+
+## Day 14
+
+```
+Year2015::Day14
+  when Part 1
+    gives a final result
+  when Part 2
+    gives a final result
+  when Results
+    correctly answers part 1
+    correctly answers part 2
+```
+
+This day doesn't have complicated concepts. If you want to dig, you can think of each reindeer as a [finite-state machine](https://en.wikipedia.org/wiki/Finite-state_machine), which is [one of the concepts that are best solved thanks to Object-oriented programming](https://eev.ee/blog/2013/03/03/the-controller-pattern-is-awful-and-other-oo-heresy/).

year_2015/day_14.rb

@@ -0,0 +1,62 @@
+class Year2015
+  class Day14
+    class Reindeer
+      attr_reader :name, :curpos
+      attr_accessor :points
+
+      def initialize(input_line)
+        input_line =~ /(\w+) can fly (\d+) km\/s for (\d+) seconds, but then must rest for (\d+) seconds./
+        @name = $1
+        @speed = $2.to_i
+        @length = $3.to_i
+        @rest = $4.to_i
+        @curpos = 0
+        @state = 'RUNNING'
+        @progress = 0
+        @points = 0
+      end
+
+      def switch_state(new_state)
+        @state = new_state
+        @progress = 0
+      end
+
+      def advance(kms = 1)
+        1.upto(kms) do
+          @progress += 1
+          if @state == 'RUNNING'
+            @curpos += @speed
+            switch_state('RESTING') if @progress == @length
+          elsif @progress == @rest
+            switch_state('RUNNING')
+          end
+        end
+        curpos
+      end
+    end
+
+    def initialize(input_data, input_part_one = false)
+      @input_file = input_data
+      @version = input_part_one ? 1 : 2
+      @reindeers = input_data.chomp.split("\n").map do |input_line|
+        Reindeer.new(input_line)
+      end
+    end
+
+    def simple_to_i(kms = 1)
+      @reindeers.map{|reindeer| reindeer.advance(kms) }.max
+    end
+
+    def to_i(kms = 1)
+      return simple_to_i(kms) if @version == 1
+
+      0.upto(kms) do
+        lead = @reindeers.map(&:advance).max
+        @reindeers.select{|reindeer| reindeer.curpos == lead }.each do |reindeer|
+          reindeer.points += 1
+        end
+      end
+      @reindeers.map(&:points).max
+    end
+  end
+end