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annotate day13b.rb @ 29:739415015d27

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Implement Day 20 switches part 1
author IBBoard <dev@ibboard.co.uk>
date Wed, 03 Jan 2024 11:35:22 +0000
parents fac484765bc9
children
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20
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1 #! /usr/bin/env ruby
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2
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3 if ARGV.length != 1
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4 abort("Incorrect arguments - needs input file")
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5 elsif not File.exist? (ARGV[0])
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6 abort("File #{ARGV[0]} did not exist")
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7 end
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8
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9 file = ARGV[0]
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10
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11 maps = File.open(file, "r").each_line().map(&:chomp).chunk_while {|before, after| before.length == after.length}.filter {|chunk| chunk != [""]}.map {|chunk| chunk.map{|row| row.each_char.to_a}}
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12
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13 def count_num_changes(row_a, row_b)
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14 row_a.zip(row_b).map {|a,b| (a != b) ? 1 : 0}.sum
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15 end
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16
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17 def find_imperfect_reflection(data)
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18 candidate_start = data.each_cons(2).with_index.flat_map {|vals,idx| count_num_changes(*vals) <= 1 ? [idx] : []}
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19 valid_starts = candidate_start.flat_map do |start|
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20 pos = start
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21 reflected = start + 1
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22 num_changes = count_num_changes(data[pos], data[reflected])
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23 while pos > 0 and reflected < data.length - 1
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24 pos -= 1
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25 reflected += 1
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26 num_changes_in_row = count_num_changes(data[pos], data[reflected])
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27 num_changes += num_changes_in_row
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28 break unless num_changes <= 1
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29 end
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30 num_changes == 1 ? [start + 1] : []
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31 end
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32 valid_starts[0]
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33 end
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34
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35 puts maps.flat_map {|data| [find_imperfect_reflection(data).to_i * 100, find_imperfect_reflection(data.transpose()).to_i]}.sum