day 15

Author: bseverac

2020/day13/main.rb

@@ -33,7 +33,7 @@ def find_pair_match(result, b, offset)
   { first: time, period: a * b }
 end
 
-class Day12Test < Test::Unit::TestCase
+class Day13Test < Test::Unit::TestCase
   def test_star_1
     data = extract_data('data_test.txt')
     assert_equal 295, resolve_1(data)

2020/day14/main.rb

@@ -7,7 +7,7 @@ def extract_data(name)
   File.read(name).split("\n")
 end
 
-class Day12
+class Day14
   def initialize
     @mask = ''
     @memory = {}
@@ -43,9 +43,9 @@ def sum
 end
 
 
-class Day12Test < Test::Unit::TestCase
+class Day14Test < Test::Unit::TestCase
   def test_star_1
-    d = Day12.new
+    d = Day14.new
     assert_equal(
       73,
       d.exec_mask(
@@ -57,28 +57,28 @@ def test_star_1
 
   def test_star_1_test
     data = extract_data('data_test.txt')
-    d = Day12.new
+    d = Day14.new
     data.each { |line| d.play(line, "*") }
     assert_equal 165, d.sum
   end
 
   def test_star_1
     data = extract_data('data.txt')
-    d = Day12.new
+    d = Day14.new
     data.each { |line| d.play(line, "*") }
     assert_equal 4297467072083, d.sum
   end
 
   def test_star_2
     data = extract_data('data_test2.txt')
-    d = Day12.new
+    d = Day14.new
     data.each { |line| d.play(line, "**") }
     assert_equal 208, d.sum
   end
 
   def test_star_2_final
     data = extract_data('data.txt')
-    d = Day12.new
+    d = Day14.new
     data.each { |line| d.play(line, "**") }
     assert_equal 5030603328768, d.sum
   end

2020/day15/main.rb

@@ -0,0 +1,54 @@
+#!/usr/bin/ruby
+require 'matrix'
+require 'test/unit'
+require 'pry'
+class Day15
+  def initialize(list)
+    @previous = list
+    @memory = {}
+    list.each_with_index do |e, index|
+      @memory[e] ||= []
+      @memory[e] << index + 1
+    end
+  end
+
+  def loop(times)
+    (times - @previous.count).times { |_| self.step }
+    self
+  end
+
+  def step
+    previous = @previous[-1]
+    if @memory[previous]
+      @memory[previous] << @previous.length
+      @previous << @memory[previous].last(2).inject(:-).abs
+    else
+      @memory[previous] = [@previous.length]
+      @previous << 0
+    end
+  end
+
+  def result
+    @previous[-1]
+  end
+end
+
+class Day12Test < Test::Unit::TestCase
+  def test_star_1_test_2
+    assert_equal 436,   Day15.new([0,3,6]).loop(2020).result
+    assert_equal 1,     Day15.new([1,3,2]).loop(2020).result
+    assert_equal 10,    Day15.new([2,1,3]).loop(2020).result
+    assert_equal 27,    Day15.new([1,2,3]).loop(2020).result
+    assert_equal 78,    Day15.new([2,3,1]).loop(2020).result
+    assert_equal 438,   Day15.new([3,2,1]).loop(2020).result
+    assert_equal 1836,  Day15.new([3,1,2]).loop(2020).result
+  end
+
+  def test_star_1_final
+    assert_equal 289,     Day15.new([0,8,15,2,12,1,4]).loop(2020).result
+  end
+
+  def test_star_2_final
+    assert_equal 1505722, Day15.new([0,8,15,2,12,1,4]).loop(30000000).result
+  end
+end