Day 23 part 1 Ruby solution

Author: creideiki

23-1.rb

@@ -0,0 +1,262 @@
+#!/usr/bin/env ruby
+
+require 'algorithms'  # https://github.com/kanwei/algorithms v1.0.0
+
+class State
+  attr_accessor :energy
+  attr_accessor :hallway
+  attr_accessor :rooms
+  attr_accessor :solution
+
+  def to_s
+    s  = "Energy: #{@energy}\n"
+    s += "Moves: #{@solution}\n"
+    s += '#############' + "\n"
+    s += '#'
+    @hallway.each_with_index do |h, pos|
+      s += '.' if pos.between?(2, 5)
+      s += (h or '.')
+    end
+    s += '#' + "\n"
+    s += '##'
+    @rooms.each { |r| s += '#' + (r[0] or '.') }
+    s += '###' + "\n"
+    s += '  '
+    @rooms.each { |r| s += '#' + (r[1] or '.') }
+    s += '#' + "\n"
+    s += '  #########' + "\n"
+    s
+  end
+
+  alias inspect to_s
+
+  @@cost = {
+    'A' => 1,
+    'B' => 10,
+    'C' => 100,
+    'D' => 1000
+  }
+
+  @@destination = {
+    'A' => 0,
+    'B' => 1,
+    'C' => 2,
+    'D' => 3
+  }
+
+  @@hallway_coords = {
+    0 => 0,
+    1 => 1,
+    2 => 3,
+    3 => 5,
+    4 => 7,
+    5 => 9,
+    6 => 10
+  }
+
+  @@room_coords = {
+    0 => 2,
+    1 => 4,
+    2 => 6,
+    3 => 8
+  }
+
+  def hallway_out_distance(room, hallway)
+    d = 3 - @rooms[room].size
+    d += (@@hallway_coords[hallway] - @@room_coords[room]).abs
+    d
+  end
+
+  def hallway_in_distance(room, hallway)
+    d = 2 - @rooms[room].size
+    d += (@@hallway_coords[hallway] - @@room_coords[room]).abs
+    d
+  end
+
+  def room_distance(source, dest)
+    d = 3 - @rooms[source].size
+    d += (@@room_coords[source] - @@room_coords[dest]).abs
+    d += 2 - @rooms[dest].size
+  end
+
+  def initialize(rooms)
+    @energy = 0
+    @hallway = [nil] * 7
+    @rooms = rooms.map(&:dup)
+    @solution = []
+  end
+
+  def initialize_copy(other)
+    @energy = other.energy
+    @hallway = other.hallway.dup
+    @rooms = other.rooms.map(&:dup)
+    @solution = other.solution.dup
+  end
+
+  def hash
+    s = @hallway.map { |p| p == nil ? '0' : p }
+    s += @rooms.map do |room|
+      case room.size
+      when 0
+        '00'
+      when 1
+        '0' + room[0]
+      when 2
+        room[0] + room[1]
+      end
+    end
+    s.join('').to_i(16)
+  end
+
+  def finished?
+    finished = hallway.all? nil
+    rooms.each_index do |position|
+      finished &&= @rooms[position].all? do |amphipod|
+        position == @@destination[amphipod]
+      end
+    end
+    finished
+  end
+
+  def ==(other)
+    @hallway == other.hallway and @rooms == other.rooms and @energy == other.energy
+  end
+
+  alias eql? ==
+
+  def moves
+    possible_moves = []
+
+    # Is there space in the destination rooms?
+    valid_target_room = [true] * 4
+    @rooms.each_with_index do |occupants, room_no|
+      valid_target_room[room_no] &&= occupants.size < 2
+      valid_target_room[room_no] &&= occupants.all? { |amphipod| room_no == @@destination[amphipod] }
+    end
+
+    # Is the hallway clear?
+    clear_hallway = @hallway.map(&:nil?)
+    clear_hallway[0] &&= @hallway[1].nil?
+    clear_hallway[6] &&= @hallway[5].nil?
+
+    # Move amphipods out of the hallway into destination rooms
+    @hallway.each_with_index do |amphipod, hallway_position|
+      next unless amphipod
+
+      destination_room = @@destination[amphipod]
+      # Hallway positions that need to be clear for this move to be possible
+      diff = hallway_position - destination_room
+      clear_range = if diff > 2  # Crossing one or more hallways to the left
+                      destination_room + 2..hallway_position - 1
+                    elsif diff <= 0  # Crossing one or more hallways to the right
+                      hallway_position + 1..destination_room + 1
+                    elsif diff == 1 and hallway_position == 0
+                      1..2
+                    else
+                      1..0  # Room is next to hallway position, no extra clear hallway required.
+                    end
+
+      next unless amphipod and valid_target_room[destination_room] and clear_hallway[clear_range].all? true
+
+      # We have an amphipod in the hallway, the destination has
+      # space, and the hallway is clear
+      moved = self.dup
+      moved.hallway[hallway_position] = nil
+      moved.rooms[destination_room].unshift amphipod
+      moved.energy += hallway_in_distance(destination_room, hallway_position) * @@cost[amphipod]
+      moved.solution.append "#{amphipod}: H#{hallway_position}->R#{destination_room}"
+      possible_moves.append moved
+    end
+
+    # Move amphipods between rooms
+    @rooms.each_with_index do |amphipods, source_room|
+      next if amphipods.empty?
+      # No amphipod will move out of this room
+      next if amphipods.all? { |a| source_room == @@destination[a] }
+
+      amphipod = amphipods[0]
+      destination_room = @@destination[amphipod]
+      # Hallway positions that need to be clear for this move to be possible
+      clear_range = if destination_room > source_room
+                      source_room + 2..destination_room + 1
+                    elsif destination_room < source_room
+                      destination_room + 2..source_room + 1
+                    end
+
+      next unless valid_target_room[destination_room] and clear_hallway[clear_range].all? true
+
+      # We have an amphipod in the wrong room, the destination has
+      # space, and the hallway is clear
+      moved = self.dup
+      moved.rooms[source_room].shift
+      moved.rooms[destination_room].unshift amphipod
+      moved.energy += room_distance(source_room, destination_room) * @@cost[amphipod]
+      moved.solution.append "#{amphipod}: R#{source_room}->R#{destination_room}"
+      possible_moves.append moved
+    end
+
+    # Move amphipods out of rooms into the hallway
+    @rooms.each_with_index do |amphipods, source_room|
+      next if amphipods.empty?
+
+      # No amphipod in this room can move out
+      next if amphipods.all? { |a| source_room == @@destination[a] }
+
+      amphipod = amphipods[0]
+      0.upto(6) do |hallway_position|
+        # Hallway positions that need to be clear for this move to be possible
+        diff = hallway_position - source_room
+        clear_range = if diff > 2  # Crossing one or more hallways to the left
+                        source_room + 2..hallway_position - 1
+                      elsif diff <= 0  # Crossing one or more hallways to the right
+                        hallway_position..source_room + 1
+                      elsif diff == 1 and hallway_position == 0
+                        1..2
+                      else
+                        1..0  # Room is next to hallway position, no extra clear hallway required.
+                      end
+
+        next unless clear_hallway[hallway_position] and clear_hallway[clear_range].all? true
+
+        # We have an amphipod in the wrong room, and the hallway is clear
+        moved = self.dup
+        moved.rooms[source_room].shift
+        moved.hallway[hallway_position] = amphipod
+        moved.energy += hallway_out_distance(source_room, hallway_position) * @@cost[amphipod]
+        moved.solution.append "#{amphipod}: R#{source_room}->H#{hallway_position}"
+        possible_moves.append moved
+      end
+    end
+
+    possible_moves
+  end
+end
+
+map = File.read('23.input').lines.map(&:strip)
+
+rooms = []
+0.upto(3) do |i|
+  rooms.append [map[2].delete('#')[i], map[3].delete('#')[i]]
+end
+
+start = State.new rooms
+visited = Hash.new false
+
+queue = Containers::MinHeap.new
+queue.push(start.energy, start)
+
+until queue.empty?
+  state = queue.pop
+
+  if state.finished?
+    print state.energy, "\n"
+    exit
+  end
+
+  state.moves.each do |move|
+    unless visited.has_key? move
+      queue.push(move.energy, move)
+      visited[move] = true
+    end
+  end
+end