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day23.cr
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day23.cr
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require "./priority_queue"
alias Pod = Tuple(Int8, Int8, Char)
def goal?(state)
pods, _ = state
pods.empty?
end
def estimate(pods : Array(Pod))
a = b = c = d = 0
s = pods.sum do |pod|
case pod[2]
when 'A'
a += 1
dy = (pod[1] - 3).abs
dx = dy > 0 ? pod[0] : 0
(a - 1 + dx + dy)
when 'B'
b += 1
dy = (pod[1] - 5).abs
dx = dy > 0 ? pod[0] : 0
(b - 1 + dx + dy) * 10
when 'C'
c += 1
dy = (pod[1] - 7).abs
dx = dy > 0 ? pod[0] : 0
(c - 1 + dx + dy) * 100
when 'D'
d += 1
dy = (pod[1] - 9).abs
dx = dy > 0 ? pod[0] : 0
(d - 1 + dx + dy) * 1000
else raise "wtf"
end
end
end
def in_hallway?(pod)
pod.first == 1
end
def valid_hallway_positions(pods, pod)
return if pods.any? { |p| p[1] == pod[1] && p[0] < pod[0] }
{1i8, 2i8, 4i8, 6i8, 8i8, 10i8, 11i8}.each do |dest_column|
range = pod[1] < dest_column ? (pod[1] + 1)..dest_column : dest_column...pod[1]
next if pods.any? { |p| in_hallway?(p) && range.includes?(p[1]) }
yield(1i8, dest_column)
end
end
def dist(x, y, xnew, ynew)
(xnew - x).abs + (ynew - y).abs
end
def cost(c, dist)
case c
when 'A' then 1 * dist
when 'B' then 10 * dist
when 'C' then 100 * dist
when 'D' then 1000 * dist
else raise "wtf"
end
end
def dest_column(pod)
x, y, c = pod
case c
when 'A' then 3i8
when 'B' then 5i8
when 'C' then 7i8
when 'D' then 9i8
else raise "hfud"
end
end
def find_valid_dest_position(pods, pod)
dest_column = dest_column(pod)
range = pod[1] > dest_column ? dest_column...pod[1] : (pod[1] + 1)..dest_column
return if pods.any? { |p| in_hallway?(p) && range.includes?(p[1]) || p[1] == dest_column }
count = pods.count { |p| p[2] == pod[2] }
yield(count.to_i8 + 1, dest_column)
end
def neighbours(state)
pods, cost = state
pods.each_with_index do |(x, y, c), i|
pod = {x, y, c}
if in_hallway?(pod)
find_valid_dest_position(pods, pod) do |xnew, ynew|
distance = dist(x, y, xnew, ynew)
new_pods = pods.dup
new_pods.delete_at(i)
newcost = cost + cost(c, distance)
yield({new_pods, newcost, estimate(new_pods)})
end
else
valid_hallway_positions(pods, pod) do |xnew, ynew|
new_pods = pods.dup
distance = dist(x, y, xnew, ynew)
new_pods[i] = {xnew, ynew, c}
newcost = cost + cost(c, distance)
yield(new_pods.sort!, newcost, newcost + estimate(new_pods))
end
end
end
end
def read_pods(chars)
pods = Array(Pod).new
chars.each_with_index do |r, x|
r.each_with_index do |c, y|
pods << {x.to_i8, y.to_i8, c} if c.in?('A', 'B', 'C', 'D')
end
end
pods
end
def solve(pods)
queue = PriorityQueue(Int32, Tuple(Array(Pod), Int32)).new
queue.insert({pods.sort!, 0}, estimate(pods))
seen = Set(Array(Pod)).new
while state = queue.pull
last = state
break if goal?(state)
neighbours(state) do |pods, cost, estimate|
next if seen.includes?(pods)
seen << pods
queue.insert({pods, cost}, estimate)
end
end
last[1] if last
end
input = File.read("input.day23")
chars = input.lines.map(&.chars)
part1 = read_pods(chars)
chars = chars[0..2] + [
" #D#C#B#A#".chars,
" #D#B#A#C#".chars,
] + chars[3..]
part2 = read_pods(chars)
puts "part 1: #{solve(part1)}"
puts "part 2: #{solve(part2)}"