Year 2016: Day 08

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 07](year_2016.md)
+* [2016, up to day 08](year_2016.md)
 * [2023, up to day 03](year_2023.md)
 
 # How to use

spec/year_2016/day_08_input

@@ -0,0 +1,170 @@
+rect 1x1
+rotate row y=0 by 5
+rect 1x1
+rotate row y=0 by 5
+rect 1x1
+rotate row y=0 by 3
+rect 1x1
+rotate row y=0 by 2
+rect 1x1
+rotate row y=0 by 3
+rect 1x1
+rotate row y=0 by 2
+rect 1x1
+rotate row y=0 by 5
+rect 1x1
+rotate row y=0 by 5
+rect 1x1
+rotate row y=0 by 3
+rect 1x1
+rotate row y=0 by 2
+rect 1x1
+rotate row y=0 by 3
+rect 2x1
+rotate row y=0 by 2
+rect 1x2
+rotate row y=1 by 5
+rotate row y=0 by 3
+rect 1x2
+rotate column x=30 by 1
+rotate column x=25 by 1
+rotate column x=10 by 1
+rotate row y=1 by 5
+rotate row y=0 by 2
+rect 1x2
+rotate row y=0 by 5
+rotate column x=0 by 1
+rect 4x1
+rotate row y=2 by 18
+rotate row y=0 by 5
+rotate column x=0 by 1
+rect 3x1
+rotate row y=2 by 12
+rotate row y=0 by 5
+rotate column x=0 by 1
+rect 4x1
+rotate column x=20 by 1
+rotate row y=2 by 5
+rotate row y=0 by 5
+rotate column x=0 by 1
+rect 4x1
+rotate row y=2 by 15
+rotate row y=0 by 15
+rotate column x=10 by 1
+rotate column x=5 by 1
+rotate column x=0 by 1
+rect 14x1
+rotate column x=37 by 1
+rotate column x=23 by 1
+rotate column x=7 by 2
+rotate row y=3 by 20
+rotate row y=0 by 5
+rotate column x=0 by 1
+rect 4x1
+rotate row y=3 by 5
+rotate row y=2 by 2
+rotate row y=1 by 4
+rotate row y=0 by 4
+rect 1x4
+rotate column x=35 by 3
+rotate column x=18 by 3
+rotate column x=13 by 3
+rotate row y=3 by 5
+rotate row y=2 by 3
+rotate row y=1 by 1
+rotate row y=0 by 1
+rect 1x5
+rotate row y=4 by 20
+rotate row y=3 by 10
+rotate row y=2 by 13
+rotate row y=0 by 10
+rotate column x=5 by 1
+rotate column x=3 by 3
+rotate column x=2 by 1
+rotate column x=1 by 1
+rotate column x=0 by 1
+rect 9x1
+rotate row y=4 by 10
+rotate row y=3 by 10
+rotate row y=1 by 10
+rotate row y=0 by 10
+rotate column x=7 by 2
+rotate column x=5 by 1
+rotate column x=2 by 1
+rotate column x=1 by 1
+rotate column x=0 by 1
+rect 9x1
+rotate row y=4 by 20
+rotate row y=3 by 12
+rotate row y=1 by 15
+rotate row y=0 by 10
+rotate column x=8 by 2
+rotate column x=7 by 1
+rotate column x=6 by 2
+rotate column x=5 by 1
+rotate column x=3 by 1
+rotate column x=2 by 1
+rotate column x=1 by 1
+rotate column x=0 by 1
+rect 9x1
+rotate column x=46 by 2
+rotate column x=43 by 2
+rotate column x=24 by 2
+rotate column x=14 by 3
+rotate row y=5 by 15
+rotate row y=4 by 10
+rotate row y=3 by 3
+rotate row y=2 by 37
+rotate row y=1 by 10
+rotate row y=0 by 5
+rotate column x=0 by 3
+rect 3x3
+rotate row y=5 by 15
+rotate row y=3 by 10
+rotate row y=2 by 10
+rotate row y=0 by 10
+rotate column x=7 by 3
+rotate column x=6 by 3
+rotate column x=5 by 1
+rotate column x=3 by 1
+rotate column x=2 by 1
+rotate column x=1 by 1
+rotate column x=0 by 1
+rect 9x1
+rotate column x=19 by 1
+rotate column x=10 by 3
+rotate column x=5 by 4
+rotate row y=5 by 5
+rotate row y=4 by 5
+rotate row y=3 by 40
+rotate row y=2 by 35
+rotate row y=1 by 15
+rotate row y=0 by 30
+rotate column x=48 by 4
+rotate column x=47 by 3
+rotate column x=46 by 3
+rotate column x=45 by 1
+rotate column x=43 by 1
+rotate column x=42 by 5
+rotate column x=41 by 5
+rotate column x=40 by 1
+rotate column x=33 by 2
+rotate column x=32 by 3
+rotate column x=31 by 2
+rotate column x=28 by 1
+rotate column x=27 by 5
+rotate column x=26 by 5
+rotate column x=25 by 1
+rotate column x=23 by 5
+rotate column x=22 by 5
+rotate column x=21 by 5
+rotate column x=18 by 5
+rotate column x=17 by 5
+rotate column x=16 by 5
+rotate column x=13 by 5
+rotate column x=12 by 5
+rotate column x=11 by 5
+rotate column x=3 by 1
+rotate column x=2 by 5
+rotate column x=1 by 5
+rotate column x=0 by 1

spec/year_2016/day_08_sample_one

@@ -0,0 +1,4 @@
+rect 3x2
+rotate column x=1 by 1
+rotate row y=0 by 4
+rotate column x=1 by 1

spec/year_2016/day_08_spec.rb

@@ -0,0 +1,23 @@
+require 'year_2016/day_08'
+
+describe Year2016::Day08 do
+  context 'when Part 1' do
+    subject(:sample_one) do
+      File.read('spec/year_2016/day_08_sample_one')
+    end
+
+    it 'gives a final result' do
+      expect(described_class.new(sample_one).to_i).to eq(6)
+    end
+  end
+
+  context 'when Results' do
+    subject(:input_data) do
+      File.read('spec/year_2016/day_08_input')
+    end
+
+    it 'correctly answers part 1' do
+      expect(described_class.new(input_data).to_i).to eq(106)
+    end
+  end
+end

year_2016.md

@@ -101,3 +101,17 @@ Year2016::Day07
 ```
 
 Again, `Enumerable` to the rescue. The method [`#each_cons`](https://ruby-doc.org/core-3.0.1/Enumerable.html#method-i-each_cons) is perfect for the kind fo look-ahead we require here.
+
+## Day 08: Two-Factor Authentication
+
+```
+Year2016::Day08
+  when Part 1
+    gives a final result
+  when Results
+    correctly answers part 1
+```
+
+This time, `Array` saves us with [`#rotate`](https://ruby-doc.org/core-3.0.1/Array.html#method-i-rotate). Be careful: the rotation is from beginning to end, so the LAST element becomes first for every rotation, which isn't the most intuitive way to do this (first element becomes second feels more intuitive, no?).
+
+Second part will have to be read on your own.

year_2016/day_02.rb

@@ -59,7 +59,6 @@ def do_moves(starter, line)
 
     def code
       @code ||= @input.split("\n").each_with_object([]) do |line, code|
-        # puts "=> #{code[-1] || '?'} => #{line}"
         result = do_moves(code[-1] || '5', line)
 
         code << result

year_2016/day_08.rb

@@ -0,0 +1,52 @@
+class Year2016
+  class Day08
+    def initialize(input_data)
+      @table = Array.new(6){ Array.new(50, '.') }
+      input_data.chomp.split("\n").each do |instruction|
+        interpret(instruction)
+      end
+    end
+
+    def interpret(instruction)
+      case instruction
+      when /^rect (\d+)x(\d+)$/
+        rect($1.to_i, $2.to_i)
+      when /^rotate row y=(\d+) by (\d+)/
+        rotate_row($1.to_i, $2.to_i)
+      when /^rotate column x=(\d+) by (\d+)/
+        rotate_column($1.to_i, $2.to_i)
+      else
+        raise "Invalid instruction: #{instruction}"
+      end
+    end
+
+    def rect(width, height)
+      0.upto(height - 1) do |idx|
+        @table[idx][0..(width - 1)] = Array.new(width, '#')
+      end
+    end
+
+    def rotate_row(row, len)
+      @table[row] = @table[row].rotate(len * - 1)
+    end
+
+    def rotate_column(column, len)
+      full_columns = @table.map{|row| row[column] }.rotate(len * -1)
+      full_columns.each_with_index do |char, idx|
+        @table[idx][column] = char
+      end
+    end
+
+    def to_i
+      @table.flatten.count('#')
+    end
+
+    def to_s
+      @table.map(&:join).join("\n")
+    end
+
+    def code
+      'CFLELOYFCS'
+    end
+  end
+end