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annotate day6b.rb @ 33:676461cc3a70

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Day 23 - track segments, not each space This allows us to explore the branches once then do quicker calculations for valid route lengths. But still requires exploring 1,262,816 routes to find the longest!
author IBBoard <dev@ibboard.co.uk>
date Thu, 04 Jan 2024 14:52:24 +0000
parents 6e0615e54e71
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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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