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annotate day6b.rb @ 24:19481b061461

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Implement tilting and cycling for Day 14 part 2 Lots of false starts trying to iterate. Eventually looked for "back in same position" to spot a loop. Then took longer to spot that "same position" isn't necessarily "start position" and loop can be offset!
author IBBoard <dev@ibboard.co.uk>
date Sat, 16 Dec 2023 20:39:02 +0000
parents 6e0615e54e71
children
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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 time, distance = File.open(file, "r").each_line(chomp: true).map {|v| v.split(":")[1].split(" ").join("").to_i}
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12 events = [[time, distance]]
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13
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14 product = events.map do |event|
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15 mid = (event[0].to_f / 2).floor
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16 first_success = (1..mid).bsearch {|i| (event[0] - i) * i > event[1]}
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17 num_success = (mid - first_success + 1) * 2
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18 event[0].odd? ? num_success : num_success - 1
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19 end.reduce(:*)
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20
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21 puts product