Day 17 part 1

Gemfile

@@ -5,5 +5,6 @@ source 'https://rubygems.org'
 gem 'colorize'
 gem 'debug'
 gem 'minitest'
+gem 'priority_queue_cxx', require: false
 gem 'rake'
 gem 'rubocop'

Gemfile.lock

@@ -3,32 +3,33 @@ GEM
   specs:
     ast (2.4.2)
     colorize (1.1.0)
-    debug (1.8.0)
-      irb (>= 1.5.0)
-      reline (>= 0.3.1)
-    io-console (0.6.0)
+    debug (1.9.0)
+      irb (~> 1.10)
+      reline (>= 0.3.8)
+    io-console (0.7.1)
     irb (1.10.1)
       rdoc
       reline (>= 0.3.8)
     json (2.7.1)
     language_server-protocol (3.17.0.3)
     minitest (5.20.0)
-    parallel (1.23.0)
+    parallel (1.24.0)
     parser (3.2.2.4)
       ast (~> 2.4.1)
       racc
+    priority_queue_cxx (0.3.6)
     psych (5.1.1.1)
       stringio
     racc (1.7.3)
     rainbow (3.1.1)
     rake (13.1.0)
-    rdoc (6.6.1)
+    rdoc (6.6.2)
       psych (>= 4.0.0)
     regexp_parser (2.8.3)
     reline (0.4.1)
       io-console (~> 0.5)
     rexml (3.2.6)
-    rubocop (1.58.0)
+    rubocop (1.59.0)
       json (~> 2.3)
       language_server-protocol (>= 3.17.0)
       parallel (~> 1.10)
@@ -42,7 +43,7 @@ GEM
     rubocop-ast (1.30.0)
       parser (>= 3.2.1.0)
     ruby-progressbar (1.13.0)
-    stringio (3.1.0)
+    stringio (3.1.1)
     unicode-display_width (2.5.0)
 
 PLATFORMS
@@ -54,6 +55,7 @@ DEPENDENCIES
   colorize
   debug
   minitest
+  priority_queue_cxx
   rake
   rubocop
 

app.rb

@@ -6,4 +6,5 @@
 require 'bundler/setup'
 require './lib/runner'
 require './lib/bench'
+require './lib/util'
 Dir['./lib/days/*.rb'].each { |f| require f }

examples/17.txt

@@ -0,0 +1,13 @@
+2413432311323
+3215453535623
+3255245654254
+3446585845452
+4546657867536
+1438598798454
+4457876987766
+3637877979653
+4654967986887
+4564679986453
+1224686865563
+2546548887735
+4322674655533

lib/days/14.rb

@@ -70,15 +70,6 @@ def rotate_clockwise(grid)
     new_grid
   end
 
-  def print_grid(grid)
-    grid.first.length.times do |y|
-      grid.length.times do |x|
-        print grid[x][y]
-      end
-      print "\n"
-    end
-  end
-
   def part1(input)
     calculate(shift_grid(parse(input)))
   end

lib/days/17.rb

@@ -0,0 +1,105 @@
+class Day17
+  require 'fc'
+  include Util
+
+  Crucible = Struct.new(
+    :x, :y, :cost, :dir, :moves_in_dir
+  ) do
+
+    def pos
+      [x, y]
+    end
+  end
+
+  def part1(input)
+    grid = parse_grid(input, :to_i)
+    goal = [grid.length - 1, grid.first.length - 1]
+
+    queue = FastContainers::PriorityQueue.new(:min)
+    queue.push(Crucible.new(0, 0, 0, :down, 0), 0)
+    visited = Set.new
+
+    loop do
+      crucible = queue.top
+      queue.pop
+
+      return crucible.cost if crucible.pos == goal
+
+      next_steps = available_moves(grid, crucible.pos, crucible.cost, crucible.dir, crucible.moves_in_dir)
+
+      next_steps.each do |next_step|
+        hash = [next_step.pos, next_step.dir, next_step.moves_in_dir]
+        next if visited.include?(hash)
+
+        visited.add(hash)
+        queue.push(next_step, next_step.cost)
+      end
+
+      break if queue.none?
+    end
+  end
+
+  LEFT_TO_RIGHT = :right
+  RIGHT_TO_LEFT = :left
+  DOWN = :down
+  UP = :up
+
+  def available_moves(grid, position, current_cost, current_direction, num_direction)
+    moves = []
+
+    if position[1] != grid.first.length - 1 &&
+       current_direction != UP &&
+       !(current_direction == DOWN && num_direction >= 3)
+
+      moves << Crucible.new(
+        position[0],
+        position[1] + 1,
+        current_cost + grid[position[0]][position[1] + 1],
+        DOWN,
+        current_direction == DOWN ? num_direction + 1 : 1)
+    end
+
+    if !position[1].zero? &&
+       current_direction != DOWN &&
+       !(current_direction == UP && num_direction >= 3)
+
+      moves << Crucible.new(
+        position[0],
+        position[1] - 1,
+        current_cost + grid[position[0]][position[1] - 1],
+        UP,
+        current_direction == UP ? num_direction + 1 : 1)
+    end
+
+    if position[0] != grid.length - 1 &&
+       current_direction != RIGHT_TO_LEFT &&
+       !(current_direction == LEFT_TO_RIGHT && num_direction >= 3)
+
+      moves << Crucible.new(
+        position[0] + 1,
+        position[1],
+        current_cost + grid[position[0] + 1][position[1]],
+        LEFT_TO_RIGHT,
+        current_direction == LEFT_TO_RIGHT ? num_direction + 1 : 1)
+    end
+
+    if !position[0].zero? &&
+       current_direction != LEFT_TO_RIGHT &&
+       !(current_direction == RIGHT_TO_LEFT && num_direction >= 3)
+
+      moves << Crucible.new(
+        position[0] - 1,
+        position[1],
+        current_cost + grid[position[0] - 1][position[1]],
+        RIGHT_TO_LEFT,
+        current_direction == RIGHT_TO_LEFT ? num_direction + 1 : 1)
+    end
+
+    moves
+  end
+
+  def part2(_input)
+    'TODO'
+  end
+
+end

lib/util.rb

@@ -0,0 +1,28 @@
+module Util
+  def parse_grid(input, fn = nil)
+    lines = input.split("\n")
+    grid = []
+
+    lines.length.times do |n|
+      lines[n].chars.each_with_index do |char, i|
+        grid[i] ||= []
+        grid[i] << (fn ? char.send(fn) : char)
+      end
+    end
+
+    grid
+  end
+
+  def print_grid(grid)
+    grid.first.length.times do |y|
+      grid.length.times do |x|
+        print grid[x][y]
+      end
+      print "\n"
+    end
+  end
+
+  def percent(x, y)
+    "#{(x / y.to_f * 100).round(1)}%"
+  end
+end

test/17_test.rb

@@ -0,0 +1,18 @@
+require 'minitest/autorun'
+require 'minitest/pride'
+require_relative '../app'
+
+class TestDay17 < Minitest::Test
+  def setup
+    @data = File.read(File.join(APP_ROOT, 'examples', '17.txt')).rstrip
+    @day = Day17.new
+  end
+
+  def test_part1
+    assert_equal @day.part1(@data), 102
+  end
+
+  def test_part2
+    assert_equal @day.part2(@data), ''
+  end
+end