Mercurial > repos > other > adventofcode2023
comparison day13.rb @ 20:fac484765bc9
Implement Day 13 mirror line finding
Walking in a loop didn't work, but consecutive pairs give a great
starting point. And there might even be a more Ruby-ish version
of the WHILE loop using zip, reverse and array ranges.
| author | IBBoard <dev@ibboard.co.uk> |
|---|---|
| date | Wed, 13 Dec 2023 20:32:13 +0000 |
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| 19:1e16a25a9553 | 20:fac484765bc9 |
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| 1 #! /usr/bin/env ruby | |
| 2 | |
| 3 if ARGV.length != 1 | |
| 4 abort("Incorrect arguments - needs input file") | |
| 5 elsif not File.exist? (ARGV[0]) | |
| 6 abort("File #{ARGV[0]} did not exist") | |
| 7 end | |
| 8 | |
| 9 file = ARGV[0] | |
| 10 | |
| 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}} | |
| 12 | |
| 13 def find_reflection(data) | |
| 14 candidate_start = data.each_cons(2).with_index.flat_map {|vals,idx| a,b = vals; a == b ? [idx] : []} | |
| 15 valid_starts = candidate_start.flat_map do |start| | |
| 16 pos = start | |
| 17 reflected = start + 1 | |
| 18 match = true | |
| 19 while pos > 0 and reflected < data.length - 1 | |
| 20 pos -= 1 | |
| 21 reflected += 1 | |
| 22 match = data[pos] == data[reflected] | |
| 23 break unless match | |
| 24 end | |
| 25 match ? [start + 1] : [] | |
| 26 end | |
| 27 valid_starts[0] | |
| 28 end | |
| 29 | |
| 30 puts maps.flat_map {|data| [find_reflection(data).to_i * 100, find_reflection(data.transpose()).to_i]}.sum |