AdventOfCode-2018/day15.cr

require "./common.cr"

lines = STDIN.gets_to_end.split("\n")
lines.pop

units = [] of NamedTuple(type: Symbol, power: Int32, hp: Int32, x: Int32, y: Int32)
lines.each_with_index do |line, y|
  line.each_char_with_index do |char, x|
    units << { type: :elf, power: 3, hp: 200, x: x, y: y } if char == 'E'
    units << { type: :goblin, power: 3, hp: 200, x: x, y: y } if char == 'G'
  end
end
map = lines.map &.chars

alias Spot = NamedTuple(x: Int32, y: Int32)

def nearby_spots(map, x, y)
  spots = [] of Spot
  spots << { x: x, y: y - 1} if y > 0
  spots << { x: x - 1, y: y } if x > 0
  spots << { x: x + 1, y: y } if x < map[0].size - 1
  spots << { x: x, y: y + 1} if y < map.size - 1
  return spots
end

def all_open_spots(map, units, type)
  open_spots = [] of Spot
  units.select &.[:type].==(type)
  units.each do |unit|
    next unless unit[:type] == type
    x = unit[:x]
    y = unit[:y]

    open_spots.concat nearby_spots(map, x, y)
  end
  open_spots.select! do |spot|
    map[spot[:y]][spot[:x]] != '#'
  end
  sort_reading_order(open_spots)
  return open_spots
end

def sort_reading_order(collection)
  collection.sort_by! do |item|
    item[:y] * 100 + item[:x]
  end
end

def in_range(map, units, spot, type)
  nearby_spots(map, spot[:x], spot[:y]).select do |spot|
    units.any? { |u| u[:x] == spot[:x] && u[:y] == spot[:y] && u[:type] == type }
  end
end

def occupied(map, units, x, y)
  return (map[y][x] == '#') || units.any? { |u| (u[:x] == x) && (u[:y] == y) }
end

def filter_reachable(map, units, start_spot, open_spots)
  open_spots.select do |spot|
    shortest_path(map, units, start_spot, spot)
  end
end

def opposite_type(type)
  return :goblin if type == :elf
  return :elf
end

def dist(one, other)
  (one[:x] - other[:x]).abs + (one[:y] - other[:y]).abs
end

def path(came_from : Hash(T|R, T|R), start : R) forall T, R
  path = [ start ] of (T|R)
  while came_from.has_key? start
    start = came_from[start]
    path << start
  end
  return path.reverse!
end

def astart_path(map, units, from, to)
  done = Set(Spot).new
  open = Set(Spot).new
  start = {x: from[:x], y: from[:y] }
  open << start
  fscore = {} of Spot => Int32
  gscore = { start => 0 }
  came_from = {} of Spot => Spot
  while !open.empty?
    min = open.min_by { |spot| fscore[spot]? || 100000000 }
    return path(came_from, min) if min == to

    open.delete min
    done << min

    min_gscore = gscore[min]? || (100000000)
    nearby_spots(map, min[:x], min[:y]).select { |spot| !occupied(map, units, spot[:x], spot[:y]) }.each do |neighbor|
      next if done.includes? neighbor
      neighbor_gscore = gscore[neighbor]? || (100000000)
      new_score = min_gscore + 1
      open << neighbor if !open.includes? neighbor
      next if new_score >= neighbor_gscore


      came_from[neighbor] = min
      gscore[neighbor] = new_score
      fscore[neighbor] = new_score + (neighbor[:y] - min[:y]) * 2 + (neighbor[:x] - min[:x]) # + (dist(neighbor, to)) # + ((neighbor[:y] - min[:y]) * 10))
    end
  end
end

def shortest_path(map, units, from, to)
  visited = Set(Spot).new
  open = Deque(Spot).new(1, { x: from[:x], y: from[:y] } )
  from_hash = {} of Spot => Spot
  return [{ x: from[:x], y: from[:y] }] if from[:x] == to[:x] && from[:y] == to[:y]

  while !visited.includes?(to) && !open.empty?
    current = open.first
    open.delete current
    visited << current
    x, y = current[:x], current[:y]

    nearby_spots(map, x, y).each do |it|
      next if visited.includes? it
      visited << it
      next if occupied(map, units, it[:x], it[:y])
      from_hash[it] = current
      open << it
    end
  end
  return path(from_hash, to) if visited.includes? to
  return nil
end

def moved_unit(map, units, unit)
  all_spots = all_open_spots(map, units, opposite_type(unit[:type]))
  # puts "all spots: #{all_spots}"
  all_spots.select! do |spot|
    next true if spot[:x] == unit[:x] && spot[:y] == unit[:y]
    next !occupied(map, units, spot[:x], spot[:y])
  end
  # puts "spots not occupied: #{all_spots}"
  all_paths = all_spots.compact_map do |spot|
    shortest_path(map, units, unit, spot)
  end
  # puts "all paths: #{all_paths}"
  path = all_paths.min_by? &.size
  # puts "picked path: #{path}"
  new_spot = path.try &.[1]?
  return unit unless new_spot
  return { x: new_spot[:x], y: new_spot[:y], power: unit[:power], hp: unit[:hp], type: unit[:type] }
end

def unit_at?(units, x, y)
  units.select { |u| u[:x] == x && u[:y] == y }.first?
end

def unit_at(units, x, y)
  units.select { |u| u[:x] == x && u[:y] == y }.first
end

def attacked_unit(map, units, unit)
  all_spots = nearby_spots(map, unit[:x], unit[:y])
  enemy_spots = all_spots.select! do |spot|
    next false unless enemy = unit_at?(units, spot[:x], spot[:y])
    enemy[:type] == opposite_type(unit[:type])
  end
  return nil if enemy_spots.empty?
  min_hp = enemy_spots.min_of do |spot|
    unit_at(units, spot[:x], spot[:y])[:hp]
  end
  enemy_spots.select! do |spot|
    unit_at(units, spot[:x], spot[:y])[:hp] == min_hp
  end
  return nil if enemy_spots.empty?

  sort_reading_order(enemy_spots)
  attacked_spot = enemy_spots[0]
  attacked_index = units.index do |unit|
    unit[:x] == attacked_spot[:x] && unit[:y] == attacked_spot[:y]
  end
  return nil unless attacked_index
  attacked_unit = units[attacked_index]
  return { attacked_index, { x: attacked_unit[:x],
                             y: attacked_unit[:y],
                             power: attacked_unit[:power],
                             hp: attacked_unit[:hp] - unit[:power],
                             type: attacked_unit[:type] } }
end

def draw(map, units)
  min_x = 0
  max_x = map[0].size - 1
  min_y = 0
  max_y = map.size - 1

  (min_y..max_y).each do |y|
    (min_x..max_x).each do |x|
      unit = unit_at?(units, x, y)
      if unit
        STDOUT << ((unit[:type] == :elf) ? 'E' : 'G')
      else
        STDOUT << (map[y][x] == '#' ? '#' : '.')
      end
    end
    puts
  end
end

def step(map, units)
  sort_reading_order(units)
  index = 0
  elf_death_count = 0
  while index < units.size
    return nil if (units.count &.[:type].==(:elf)) == 0
    return nil if (units.count &.[:type].==(:goblin)) == 0 

    unit = units[index]
    unit = moved_unit(map, units, unit)
    units[index] = unit
    attacked_u = attacked_unit(map, units, unit)
    if attacked_u
      attacked_index, attacked_unit = attacked_u
      if attacked_unit[:hp] <= 0
        elf_death_count += 1 if attacked_unit[:type] == :elf
        units.delete_at attacked_index
        index -= 1 if index >= attacked_index
      else
        units[attacked_index] = attacked_unit
      end
    end
    index += 1
  end

  return elf_death_count
end

def check_win(units)
  current_winning = nil
  units.each do |u|
    if current_winning
      return nil if current_winning != u[:type]
    else
      current_winning = u[:type]
    end
  end
  return current_winning
end

def winning_score(units, type)
  units.select(&.[:type].==(type)).sum &.[:hp]
end

power = 3
loop do
  simulating_units = units.dup.map do |unit|
    next unit unless unit[:type] == :elf
    { x: unit[:x], y: unit[:y], hp: unit[:hp], type: :elf, power: power }
  end
  steps = 0
  died = false
  # draw(map, simulating_units)
  until won = check_win(simulating_units) || died
    result = step(map, simulating_units)
    if result
      steps += 1 
      died = result > 0
    end
    # draw(map, simulating_units)
    sort_reading_order(simulating_units)
    # simulating_units.each do |unit|
    #   puts "health (#{unit[:type]}): #{unit[:hp]}"
    # end
    # puts "-- (end of roun #{steps})"
  end
  puts "(power: #{power}) #{steps} * #{winning_score(simulating_units, won)} = #{steps * winning_score(simulating_units, won)}"
  break if !died && won != :goblin
  power += 1
end