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comparison day22.rb @ 31:47dc75915e91

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Implement falling/destroying blocks Implemented part 1 with supports/supported by logic. Implemented part 2 with cascades and summing counts. Code has caching so it is quick _but_ it gives an answer that's too low.
author IBBoard <dev@ibboard.co.uk>
date Wed, 03 Jan 2024 17:00:56 +0000
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30:6de4f4d5404d 31:47dc75915e91
1 #! /usr/bin/env ruby
2
3 require 'set'
4
5 if ARGV.length != 1
6 abort("Incorrect arguments - needs input file")
7 elsif not File.exist? (ARGV[0])
8 abort("File #{ARGV[0]} did not exist")
9 end
10
11 file = ARGV[0]
12
13 Block = Struct.new(:id, :x, :y, :z)
14 SupportedBy = Struct.new(:blocks, :z)
15 supports = Hash.new
16 supported_by = Hash.new
17
18 blocks = File.open(file, "r").each_line(chomp: true).with_index.map do |line, id|
19 block_start, block_end = line.split("~")
20 start_x, start_y, start_z = block_start.split(",")
21 end_x, end_y, end_z = block_end.split(",")
22 supports[id] = []
23 Block.new(id, start_x.to_i..end_x.to_i, start_y.to_i..end_y.to_i, start_z.to_i..end_z.to_i)
24 end
25
26 def height_sort(a,b)
27 if a.z.first == b.z.first
28 # Make it a stable sort
29 a.y.first == b.y.first ? a.x.first <=> b.x.first : a.y.first <=> b.y.first
30 else
31 a.z.first <=> b.z.first
32 end
33 end
34
35 blocks.sort! {|a,b| height_sort(a, b)}
36
37 def overlap?(range_1, range_2)
38 range_1.include?(range_2.first) || range_1.include?(range_2.last) || range_2.include?(range_1.first) || range_2.include?(range_1.last)
39 end
40
41 blocks.reduce([]) do |lower_blocks, block|
42 support_blocks = lower_blocks.reduce(SupportedBy.new([], 0)) do |candidate_supports, lower_block|
43 if overlap?(block.x, lower_block.x) && overlap?(block.y, lower_block.y)
44 if lower_block.z.last > candidate_supports.z
45 SupportedBy.new([lower_block], lower_block.z.last)
46 elsif lower_block.z.last == candidate_supports.z
47 candidate_supports.blocks << lower_block
48 candidate_supports
49 else
50 candidate_supports
51 end
52 else
53 candidate_supports
54 end
55 end
56 drop = block.z.first - support_blocks.z - 1
57 block.z = (support_blocks.z+1)..(support_blocks.z+block.z.size)
58 support_blocks.blocks.each {|support| supports[support.id] << block}
59 supported_by[block.id] = support_blocks.blocks
60 lower_blocks << block
61 lower_blocks
62 end
63
64 disintegratable = supports.filter {|block_id, supports_list| supports_list.all? {|supported| supported_by[supported.id].length > 1} }
65
66 puts "#{disintegratable.length} disintegratable blocks"
67
68 def find_droppers(id, supports, supported_by, dropping, cache)
69 new_drops = supports[id].filter do |block|
70 (Set.new(supported_by[block.id].map(&:id)) - dropping).length == 0
71 end
72 dropping = dropping + new_drops.map(&:id)
73 new_drops.each do |supported_block|
74 cache_key = [supported_block.id, Set.new(supported_by[supported_block.id].map(&:id)) & dropping]
75 if cache.include?(cache_key)
76 dropping += cache[cache_key]
77 #puts "Got #{cache[cache_key]} for #{cache_key}"
78 else
79 supported_droppers = find_droppers(supported_block.id, supports, supported_by, dropping, cache)
80 cache[cache_key] = supported_droppers
81 #puts "Caching #{supported_droppers} for #{cache_key} while dropping #{dropping}"
82 dropping += supported_droppers
83 end
84 end
85 dropping - [id]
86 end
87
88 cascade = Hash.new
89 cache = Hash.new
90
91 blocks.reverse.each do |block|
92 id = block.id
93 cascade[id] = find_droppers(id, supports, supported_by, Set.new([id]), cache)
94 end
95
96 puts "Dropping a total of #{cascade.values.map{|val| val.length}.sum} blocks"