170 lines
6.3 KiB
Plaintext
170 lines
6.3 KiB
Plaintext
[1]Advent of Code
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• [2][About]
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• [3][Events]
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• [4][Shop]
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• [5][Settings]
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• [6][Log Out]
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br0xen [7](AoC++) 8*
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{'year':[8]2024}
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• [9][Calendar]
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• [10][AoC++]
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• [11][Sponsors]
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• [12][Leaderboard]
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• [13][Stats]
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Our [14]sponsors help make Advent of Code possible:
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[15]Cloudsmith - Code shapes reality; now solve your next puzzle: global
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artifact management. Join our journey to shape, secure, and be the world's
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software supply chain. We overcame the impossible and became the
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improbable - now, it's inevitable.
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--- Day 5: Print Queue ---
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Satisfied with their search on Ceres, the squadron of scholars suggests
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subsequently scanning the stationery stacks of sub-basement 17.
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The North Pole printing department is busier than ever this close to
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Christmas, and while The Historians continue their search of this
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historically significant facility, an Elf operating a [16]very familiar
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printer beckons you over.
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The Elf must recognize you, because they waste no time explaining that the
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new sleigh launch safety manual updates won't print correctly. Failure to
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update the safety manuals would be dire indeed, so you offer your
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services.
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Safety protocols clearly indicate that new pages for the safety manuals
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must be printed in a very specific order. The notation X|Y means that if
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both page number X and page number Y are to be produced as part of an
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update, page number X must be printed at some point before page number Y.
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The Elf has for you both the page ordering rules and the pages to produce
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in each update (your puzzle input), but can't figure out whether each
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update has the pages in the right order.
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For example:
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47|53
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97|13
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97|61
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97|47
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75|29
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61|13
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75|53
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29|13
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97|29
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53|29
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61|53
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97|53
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61|29
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47|13
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75|47
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97|75
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47|61
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75|61
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47|29
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75|13
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53|13
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75,47,61,53,29
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97,61,53,29,13
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75,29,13
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75,97,47,61,53
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61,13,29
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97,13,75,29,47
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The first section specifies the page ordering rules, one per line. The
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first rule, 47|53, means that if an update includes both page number 47
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and page number 53, then page number 47 must be printed at some point
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before page number 53. (47 doesn't necessarily need to be immediately
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before 53; other pages are allowed to be between them.)
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The second section specifies the page numbers of each update. Because most
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safety manuals are different, the pages needed in the updates are
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different too. The first update, 75,47,61,53,29, means that the update
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consists of page numbers 75, 47, 61, 53, and 29.
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To get the printers going as soon as possible, start by identifying which
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updates are already in the right order.
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In the above example, the first update (75,47,61,53,29) is in the right
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order:
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• 75 is correctly first because there are rules that put each other page
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after it: 75|47, 75|61, 75|53, and 75|29.
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• 47 is correctly second because 75 must be before it (75|47) and every
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other page must be after it according to 47|61, 47|53, and 47|29.
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• 61 is correctly in the middle because 75 and 47 are before it (75|61
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and 47|61) and 53 and 29 are after it (61|53 and 61|29).
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• 53 is correctly fourth because it is before page number 29 (53|29).
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• 29 is the only page left and so is correctly last.
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Because the first update does not include some page numbers, the ordering
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rules involving those missing page numbers are ignored.
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The second and third updates are also in the correct order according to
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the rules. Like the first update, they also do not include every page
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number, and so only some of the ordering rules apply - within each update,
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the ordering rules that involve missing page numbers are not used.
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The fourth update, 75,97,47,61,53, is not in the correct order: it would
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print 75 before 97, which violates the rule 97|75.
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The fifth update, 61,13,29, is also not in the correct order, since it
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breaks the rule 29|13.
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The last update, 97,13,75,29,47, is not in the correct order due to
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breaking several rules.
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For some reason, the Elves also need to know the middle page number of
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each update being printed. Because you are currently only printing the
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correctly-ordered updates, you will need to find the middle page number of
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each correctly-ordered update. In the above example, the correctly-ordered
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updates are:
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75,47,61,53,29
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97,61,53,29,13
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75,29,13
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These have middle page numbers of 61, 53, and 29 respectively. Adding
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these page numbers together gives 143.
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Of course, you'll need to be careful: the actual list of page ordering
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rules is bigger and more complicated than the above example.
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Determine which updates are already in the correct order. What do you get
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if you add up the middle page number from those correctly-ordered updates?
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To begin, [17]get your puzzle input.
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Answer: [18]_____________________ [19][ [Submit] ]
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You can also [Shareon [20]Bluesky [21]Twitter [22]Mastodon] this puzzle.
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References
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Visible links
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1. https://adventofcode.com/
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2. https://adventofcode.com/2024/about
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3. https://adventofcode.com/2024/events
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4. https://cottonbureau.com/people/advent-of-code
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5. https://adventofcode.com/2024/settings
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6. https://adventofcode.com/2024/auth/logout
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7. Advent of Code Supporter
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https://adventofcode.com/2024/support
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8. https://adventofcode.com/2024
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9. https://adventofcode.com/2024
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10. https://adventofcode.com/2024/support
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11. https://adventofcode.com/2024/sponsors
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12. https://adventofcode.com/2024/leaderboard
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13. https://adventofcode.com/2024/stats
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14. https://adventofcode.com/2024/sponsors
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15. https://adventofcode.com/2024/sponsors/redirect?url=https%3A%2F%2Fcloudsmith%2Ecom%3Futm%5Fsource%3Daoc%26utm%5Fmedium%3Dsponsor%26utm%5Fcampaign%3Daoc2024
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16. https://adventofcode.com/2017/day/1
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17. https://adventofcode.com/2024/day/5/input
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20. https://bsky.app/intent/compose?text=%22Print+Queue%22+%2D+Day+5+%2D+Advent+of+Code+2024+%23AdventOfCode+https%3A%2F%2Fadventofcode%2Ecom%2F2024%2Fday%2F5
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21. https://twitter.com/intent/tweet?text=%22Print+Queue%22+%2D+Day+5+%2D+Advent+of+Code+2024&url=https%3A%2F%2Fadventofcode%2Ecom%2F2024%2Fday%2F5&related=ericwastl&hashtags=AdventOfCode
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22. javascript:void(0);
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