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annotate day4.rb @ 39:0e17e4bd97a9 default tip

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Rewrite as four-dimensional route finding The grid isn't just a 2D grid. The constraints make it 4D: * X * Y * Last direction * Number of steps in that direction By tracking all four dimensions, we can find the shortest route for _all_ combinations of the constraint. Previously, we were dropping routes that were currently longer but ended up shorter because they could take subsequent steps that other routes couldn't.
author IBBoard <dev@ibboard.co.uk>
date Sun, 22 Sep 2024 11:30:53 +0100
parents 9da7a71b313d
children
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1 #! /usr/bin/env ruby
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2
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3 require 'set'
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4
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5 if ARGV.length != 1
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6 abort("Incorrect arguments - needs input file")
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7 elsif not File.exist? (ARGV[0])
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8 abort("File #{ARGV[0]} did not exist")
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9 end
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10
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11 file = ARGV[0]
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12
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13 sum = 0
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14 File.open(file, "r").each_line(chomp: true) do |line|
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15 winning_number_str, our_number_str = line.split(":")[1].split("|").map(&:chomp)
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16 winning_numbers = Set.new(winning_number_str.split(" ").map(&:to_i))
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17 our_numbers = Set.new(our_number_str.split(" ").map(&:to_i))
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18 our_winning_numbers = winning_numbers & our_numbers
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19 sum += our_winning_numbers.length > 0 ? 2 ** (our_winning_numbers.length - 1) : 0
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20 end
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21
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22 puts sum