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This repository was archived by the owner on Sep 20, 2025. It is now read-only.

Commit d6f5f31

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Day 18 part 2 solutions
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‎18-2.py‎

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#!/usr/bin/env python
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import numpy
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from collections import deque
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class Map:
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def __init__(self, max_x, max_y, max_z):
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self.size_x = max_x + 3
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self.size_y = max_y + 3
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self.size_z = max_z + 3
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self.map = numpy.zeros((self.size_x, self.size_y, self.size_z), dtype=numpy.uint8)
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def flood_fill(self):
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queue = deque([[0, 0, 0]])
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while len(queue) > 0:
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cell = queue.popleft()
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if self.map[cell[0], cell[1], cell[2]] != 0:
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continue
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self.map[cell[0], cell[1], cell[2]] = 2
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if cell[0] > 0 and self.map[cell[0] - 1, cell[1], cell[2]] == 0:
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queue.append([cell[0] - 1, cell[1], cell[2]])
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if cell[0] < self.size_x - 1 and self.map[cell[0] + 1, cell[1], cell[2]] == 0:
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queue.append([cell[0] + 1, cell[1], cell[2]])
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if cell[1] > 0 and self.map[cell[0], cell[1] - 1, cell[2]] == 0:
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queue.append([cell[0], cell[1] - 1, cell[2]])
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if cell[1] < self.size_y - 1 and self.map[cell[0], cell[1] + 1, cell[2]] == 0:
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queue.append([cell[0], cell[1] + 1, cell[2]])
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if cell[2] > 0 and self.map[cell[0], cell[1], cell[2] - 1] == 0:
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queue.append([cell[0], cell[1], cell[2] - 1])
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if cell[2] < self.size_z - 1 and self.map[cell[0], cell[1], cell[2] + 1] == 0:
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queue.append([cell[0], cell[1], cell[2] + 1])
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def count_exposed_faces(self):
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count = 0
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for x in range(self.size_x):
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for y in range(self.size_y):
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for z in range(self.size_z):
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if self.map[x, y, z] == 1:
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if x == 0 or self.map[x - 1, y, z] == 2:
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count += 1
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if x == self.size_x - 1 or self.map[x + 1, y, z] == 2:
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count += 1
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if y == 0 or self.map[x, y - 1, z] == 2:
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count += 1
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if y == self.size_y - 1 or self.map[x, y + 1, z] == 2:
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count += 1
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if z == 0 or self.map[x, y, z - 1] == 2:
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count += 1
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if z == self.size_z - 1 or self.map[x, y, z + 1] == 2:
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count += 1
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return count
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lines = [list(map(lambda c: int(c), line.strip().split(","))) for line in open('18.input').readlines()]
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max_x = max([x for x, _, _ in lines])
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max_y = max([y for _, y, _ in lines])
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max_z = max([z for _, _, z in lines])
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obj = Map(max_x, max_y, max_z)
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for coords in lines:
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obj.map[coords[0], coords[1], coords[2]] = 1
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obj.flood_fill()
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print(obj.count_exposed_faces())

‎18-2.rb‎

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#!/usr/bin/env ruby
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require 'numo/narray'
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class Map
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def initialize(max_x, max_y, max_z)
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@size_x = max_x + 3
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@size_y = max_y + 3
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@size_z = max_z + 3
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@map = Numo::UInt8.zeros(@size_x, @size_y, @size_z)
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end
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def [](x, y, z)
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@map[x + 1, y + 1, z + 1]
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end
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def []=(x, y, z, val)
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@map[x + 1, y + 1, z + 1] = val
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end
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def flood_fill!
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queue = [[0, 0, 0]]
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until queue.empty?
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cell = queue.shift
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next if @map[cell[0], cell[1], cell[2]] != 0
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@map[cell[0], cell[1], cell[2]] = 2
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queue << [cell[0] - 1, cell[1], cell[2]] if cell[0] > 0 and @map[cell[0] - 1, cell[1], cell[2]].zero?
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queue << [cell[0] + 1, cell[1], cell[2]] if cell[0] < @size_x - 1 and @map[cell[0] + 1, cell[1], cell[2]].zero?
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queue << [cell[0], cell[1] - 1, cell[2]] if cell[1] > 0 and @map[cell[0], cell[1] - 1, cell[2]].zero?
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queue << [cell[0], cell[1] + 1, cell[2]] if cell[1] < @size_y - 1 and @map[cell[0], cell[1] + 1, cell[2]].zero?
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queue << [cell[0], cell[1], cell[2] - 1] if cell[2] > 0 and @map[cell[0], cell[1], cell[2] - 1].zero?
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queue << [cell[0], cell[1], cell[2] + 1] if cell[2] < @size_z - 1 and @map[cell[0], cell[1], cell[2] + 1].zero?
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end
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end
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def count_exposed_faces
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count = 0
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(@size_x - 1).times do |x|
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(@size_y - 1).times do |y|
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(@size_z - 1).times do |z|
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next unless @map[x + 1, y + 1, z + 1] == 1
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count += 1 if @map[x + 1 - 1, y + 1, z + 1] == 2
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count += 1 if @map[x + 1 + 1, y + 1, z + 1] == 2
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count += 1 if @map[x + 1, y + 1 - 1, z + 1] == 2
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count += 1 if @map[x + 1, y + 1 + 1, z + 1] == 2
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count += 1 if @map[x + 1, y + 1, z + 1 - 1] == 2
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count += 1 if @map[x + 1, y + 1, z + 1 + 1] == 2
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end
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end
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end
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count
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end
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end
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input = File.read('18.input').lines.map(&:strip).map { |l| l.split(',').map(&:to_i) }
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max_x = input.map(&:first).max
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max_y = input.map { |c| c[1] }.max
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max_z = input.map(&:last).max
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map = Map.new(max_x, max_y, max_z)
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input.each do |coords|
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map[coords[0], coords[1], coords[2]] = 1
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end
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map.flood_fill!
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print map.count_exposed_faces, "\n"

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