advent-of-code/2018/ruby/day_15.rb

523 lines
9.5 KiB

require "set"
require "minitest"
require "minitest/pride"
class EndCombat < StandardError; end
class Combat
def initialize(map, elf_attack)
@map = map
@attack = {
Elf => elf_attack,
Goblin => 3,
}
end
def fight
return enum_for(__method__) unless block_given?
yield @map
loop do
turn_order.each do |pos|
next if @map[pos].nil? # don't take a turn for units that just died
turn = Turn.new(@map, pos)
if move = turn.move
unit = @map.delete(pos)
@map[move] = unit
turn.pos = move
end
if attack = turn.attack
unit = @map.fetch(turn.pos)
target = @map.fetch(attack)
target.hp -= @attack.fetch(unit.class)
@map.delete(attack) if target.hp <= 0
end
end
yield @map
end
rescue EndCombat
# yield @map
end
def turn_order
@map.units.keys.sort
end
end
class TestCombat < Minitest::Test
def test_move
map = Map.parse(<<~MAP)
#########
#G..G..G#
#.......#
#.......#
#G..E..G#
#.......#
#.......#
#G..G..G#
#########
MAP
combat = Combat.new(map, 3)
rounds = combat.fight
rounds.next # skip the first round
assert_equal <<~MAP.chomp, rounds.next.to_s
#########
#.G...G.#
#...G...#
#...E..G#
#.G.....#
#.......#
#G..G..G#
#.......#
#########
MAP
assert_equal <<~MAP.chomp, rounds.next.to_s
#########
#..G.G..#
#...G...#
#.G.E.G.#
#.......#
#G..G..G#
#.......#
#.......#
#########
MAP
assert_equal <<~MAP.chomp, rounds.next.to_s
#########
#.......#
#..GGG..#
#..GEG..#
#G..G...#
#......G#
#.......#
#.......#
#########
MAP
end
def test_fight
map = Map.parse(<<~MAP)
#######
#.G...#
#...EG#
#.#.#G#
#..G#E#
#.....#
#######
MAP
combat = Combat.new(map, 3)
rounds = combat.fight
rounds.next # skip the initial state
rounds.next # skip the first found
map = rounds.next # second round
assert_equal 188, map.fetch(Position[2,4]).hp
20.times { rounds.next }
assert_equal <<~MAP.chomp, rounds.next.to_s
#######
#...G.#
#..G.G#
#.#.#G#
#...#E#
#.....#
#######
MAP
end
def test_turn_order
map = Map.parse(<<~MAP)
#######
#.G.E.#
#E.G.E#
#.G.E.#
#######
MAP
combat = Combat.new(map, 3)
expected = [[1,2], [1,4], [2,1], [2,3], [2,5], [3,2], [3,4]].map {|pos| Position[*pos]}
assert_equal expected, combat.turn_order
end
end
class Turn
attr_accessor :pos
def initialize(map, pos)
@map, @pos = map, pos
@unit = @map.fetch(@pos)
end
def move
raise EndCombat if targets.empty?
return if can_attack?
return if nearest.empty?
chosen = nearest.min
haystack = @map.in_range(@pos)
dijkstra(chosen)
.select {|pos,_| haystack.include?(pos) }
.min_by {|pos,distance| [distance, pos] }
.first
end
def attack
attackable.min_by {|pos, target| [target.hp, pos] }&.first
end
def targets
@map.units.select {|_, other| other.is_a?(@unit.enemy) }
end
def attackable
targets.select {|pos, _| @pos.adjacent.include?(pos) }
end
def can_attack?
!attackable.empty?
end
def in_range
targets.flat_map {|pos, _| @map.in_range(pos) }.uniq
end
def reachable
dijkstra(@pos).select {|pos,_| in_range.include?(pos) }
end
def nearest
nearest = Hash.new {|h,k| h[k] = [] }
reachable.each do |pos, distance|
nearest[distance] << pos
end
return [] if nearest.empty?
nearest.min_by(&:first).last
end
private
def dijkstra(pos)
distances = { pos => 0 }
queue = [ pos ]
while pos = queue.shift
distance = distances.fetch(pos) + 1
@map.in_range(pos).reject {|pos| distances.has_key?(pos) }.each do |pos|
distances[pos] = distance
queue << pos
end
end
distances
end
end
class TestTurn < Minitest::Test
def setup
map = Map.parse(<<~MAP)
#######
#E..G.#
#...#.#
#.G.#G#
#######
MAP
@turn = Turn.new(map, Position[1,1])
end
def test_targets
assert_equal [[1,4], [3,2], [3,5]].to_set, @turn.targets.keys.map(&:to_a).to_set
end
def test_in_range
assert_equal [[1,3], [1,5], [2,2], [2,5], [3,1], [3,3]].to_set, @turn.in_range.map(&:to_a).to_set
end
def test_reachable
assert_equal [[1,3], [2,2], [3,1], [3,3]].to_set, @turn.reachable.keys.map(&:to_a).to_set
end
def test_nearest
assert_equal [[1,3], [2,2], [3,1]].to_set, @turn.nearest.map(&:to_a).to_set
end
def test_move
assert_equal Position[1,2], @turn.move
turn = Turn.new(Map.parse(<<~MAP), Position[1,2])
#######
#.E...#
#.....#
#...G.#
#######
MAP
assert_equal Position[1,3], turn.move
end
end
class Map
def self.parse(s)
occupied = {}
s.chomp.lines.each.with_index do |row, y|
row.chomp.chars.each.with_index do |square, x|
case square
when ?#
occupied[Position[y, x]] = Wall.new
when ?E
occupied[Position[y, x]] = Elf.new
when ?G
occupied[Position[y, x]] = Goblin.new
when ?.
else
fail "Invalid character: #{square.inspect}"
end
end
end
self.new(occupied)
end
def initialize(occupied)
@occupied = occupied
end
def [](pos)
@occupied[pos]
end
def []=(pos, square)
@occupied[pos] = square
end
def fetch(pos)
@occupied.fetch(pos)
end
def delete(pos)
@occupied.delete(pos)
end
def units
@occupied.select {|_, sq| sq.is_a?(Unit) }
end
def in_range(pos)
pos
.adjacent
.reject {|pos| @occupied.has_key?(pos) }
end
def to_s
max_y = @occupied.keys.map(&:y).max
max_x = @occupied.keys.map(&:x).max
(0..max_y).map {|y|
(0..max_x).map {|x|
case @occupied[Position[y, x]]
when Wall
?#
when Elf
?E
when Goblin
?G
when nil
?.
else
fail "Unexpected object: #{@occupied[Position[y, x]]}"
end
}.join
}.join(?\n)
end
end
class TestMap < Minitest::Test
def test_parse
map = Map.parse(<<~MAP)
#######
#E..G.#
#...#.#
#.G.#G#
#######
MAP
assert_instance_of Wall, map[Position[0,0]]
assert_instance_of Wall, map[Position[2,4]]
assert_instance_of Wall, map[Position[4,6]]
assert_instance_of Elf, map[Position[1,1]]
assert_instance_of Goblin, map[Position[1,4]]
assert_instance_of Goblin, map[Position[3,5]]
assert_nil map[Position[1,2]]
assert_nil map[Position[2,5]]
end
def test_units
map = Map.parse(<<~MAP)
#######
#E..G.#
#...#.#
#.G.#G#
#######
MAP
assert_equal 4, map.units.length
end
end
Position = Struct.new(:y, :x) do
def self.[](y, x)
self.new(y, x)
end
def <=>(other)
[self.y, self.x] <=> [other.y, other.x]
end
def adjacent
[-1, 1]
.flat_map {|d| [[y, x+d], [y+d, x]] }
.map {|pos| Position[*pos] }
end
def to_a
[y, x]
end
def to_s
to_a.to_s
end
end
class Unit
attr_accessor :hp
def initialize
@hp = 200
end
def to_s
"#{self.class.name.chars.first}(#{hp})"
end
end
class Wall
end
class Elf < Unit
def enemy
Goblin
end
end
class Goblin < Unit
def enemy
Elf
end
end
def solve(input)
(3..Float::INFINITY).each do |elf_attack|
map = Map.parse(input)
outcome = simulate(map, elf_attack)
next if outcome.nil?
return outcome
end
end
def simulate(map, elf_attack)
elf_count = map.units.count {|_, unit| unit.is_a?(Elf) }
combat = Combat.new(map, elf_attack)
map, count = combat.fight.map.with_index
.inject(nil) {|last,(map,count)|
return if map.units.count {|_, unit| unit.is_a?(Elf) } < elf_count
# puts map, map.units.values.map(&:to_s).inspect
[map, count]
}
return if map.units.count {|_, unit| unit.is_a?(Elf) } < elf_count
map.units.values.map(&:hp).sum * count
end
class TestSolve < Minitest::Test
def test_solve
# assert_equal 27730, solve(<<~INPUT)
assert_equal 4988, solve(<<~INPUT)
#######
#.G...#
#...EG#
#.#.#G#
#..G#E#
#.....#
#######
INPUT
# assert_equal 36334, solve(<<~INPUT)
########
##G..#E#
##E#E.E#
##G.##.#
##...#E#
##...E.#
########
#INPUT
# assert_equal 39514, solve(<<~INPUT)
assert_equal 31284, solve(<<~INPUT)
#######
#E..EG#
#.#G.E#
#E.##E#
#G..#.#
#..E#.#
#######
INPUT
# assert_equal 27755, solve(<<~INPUT)
assert_equal 3478, solve(<<~INPUT)
#######
#E.G#.#
#.#G..#
#G.#.G#
#G..#.#
#...E.#
#######
INPUT
# assert_equal 28944, solve(<<~INPUT)
assert_equal 6474, solve(<<~INPUT)
#######
#.E...#
#.#..G#
#.###.#
#E#G#G#
#...#G#
#######
INPUT
# assert_equal 18740, solve(<<~INPUT)
assert_equal 1140, solve(<<~INPUT)
#########
#G......#
#.E.#...#
#..##..G#
#...##..#
#...#...#
#.G...G.#
#.....G.#
#########
INPUT
end
end
if __FILE__ == $0
require "minitest/autorun" and exit if ENV["TEST"]
puts solve(ARGF.read)
end