158 lines
6.6 KiB
Plaintext
158 lines
6.6 KiB
Plaintext
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[1]Advent of Code
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br0xen [7](AoC++) 12*
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--- Day 6: Wait For It ---
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The ferry quickly brings you across Island Island. After asking around,
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you discover that there is indeed normally a large pile of sand somewhere
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near here, but you don't see anything besides lots of water and the small
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island where the ferry has docked.
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As you try to figure out what to do next, you notice a poster on a wall
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near the ferry dock. "Boat races! Open to the public! Grand prize is an
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all-expenses-paid trip to Desert Island!" That must be where the sand
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comes from! Best of all, the boat races are starting in just a few
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minutes.
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You manage to sign up as a competitor in the boat races just in time. The
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organizer explains that it's not really a traditional race - instead, you
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will get a fixed amount of time during which your boat has to travel as
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far as it can, and you win if your boat goes the farthest.
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As part of signing up, you get a sheet of paper (your puzzle input) that
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lists the time allowed for each race and also the best distance ever
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recorded in that race. To guarantee you win the grand prize, you need to
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make sure you go farther in each race than the current record holder.
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The organizer brings you over to the area where the boat races are held.
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The boats are much smaller than you expected - they're actually toy boats,
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each with a big button on top. Holding down the button charges the boat,
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and releasing the button allows the boat to move. Boats move faster if
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their button was held longer, but time spent holding the button counts
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against the total race time. You can only hold the button at the start of
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the race, and boats don't move until the button is released.
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For example:
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Time: 7 15 30
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Distance: 9 40 200
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This document describes three races:
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• The first race lasts 7 milliseconds. The record distance in this race
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is 9 millimeters.
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• The second race lasts 15 milliseconds. The record distance in this
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race is 40 millimeters.
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• The third race lasts 30 milliseconds. The record distance in this race
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is 200 millimeters.
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Your toy boat has a starting speed of zero millimeters per millisecond.
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For each whole millisecond you spend at the beginning of the race holding
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down the button, the boat's speed increases by one millimeter per
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millisecond.
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So, because the first race lasts 7 milliseconds, you only have a few
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options:
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• Don't hold the button at all (that is, hold it for 0 milliseconds) at
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the start of the race. The boat won't move; it will have traveled 0
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millimeters by the end of the race.
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• Hold the button for 1 millisecond at the start of the race. Then, the
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boat will travel at a speed of 1 millimeter per millisecond for 6
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milliseconds, reaching a total distance traveled of 6 millimeters.
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• Hold the button for 2 milliseconds, giving the boat a speed of 2
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millimeters per millisecond. It will then get 5 milliseconds to move,
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reaching a total distance of 10 millimeters.
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• Hold the button for 3 milliseconds. After its remaining 4 milliseconds
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of travel time, the boat will have gone 12 millimeters.
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• Hold the button for 4 milliseconds. After its remaining 3 milliseconds
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of travel time, the boat will have gone 12 millimeters.
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• Hold the button for 5 milliseconds, causing the boat to travel a total
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of 10 millimeters.
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• Hold the button for 6 milliseconds, causing the boat to travel a total
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of 6 millimeters.
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• Hold the button for 7 milliseconds. That's the entire duration of the
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race. You never let go of the button. The boat can't move until you
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let go of the button. Please make sure you let go of the button so the
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boat gets to move. 0 millimeters.
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Since the current record for this race is 9 millimeters, there are
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actually 4 different ways you could win: you could hold the button for 2,
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3, 4, or 5 milliseconds at the start of the race.
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In the second race, you could hold the button for at least 4 milliseconds
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and at most 11 milliseconds and beat the record, a total of 8 different
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ways to win.
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In the third race, you could hold the button for at least 11 milliseconds
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and no more than 19 milliseconds and still beat the record, a total of 9
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ways you could win.
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To see how much margin of error you have, determine the number of ways you
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can beat the record in each race; in this example, if you multiply these
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values together, you get 288 (4 * 8 * 9).
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Determine the number of ways you could beat the record in each race. What
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do you get if you multiply these numbers together?
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Your puzzle answer was 449820.
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--- Part Two ---
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As the race is about to start, you realize the piece of paper with race
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times and record distances you got earlier actually just has very bad
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[16]kerning. There's really only one race - ignore the spaces between the
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numbers on each line.
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So, the example from before:
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Time: 7 15 30
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Distance: 9 40 200
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...now instead means this:
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Time: 71530
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Distance: 940200
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Now, you have to figure out how many ways there are to win this single
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race. In this example, the race lasts for 71530 milliseconds and the
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record distance you need to beat is 940200 millimeters. You could hold the
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button anywhere from 14 to 71516 milliseconds and beat the record, a total
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of 71503 ways!
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How many ways can you beat the record in this one much longer race?
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Your puzzle answer was 42250895.
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Both parts of this puzzle are complete! They provide two gold stars: **
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At this point, you should [17]return to your Advent calendar and try
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another puzzle.
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If you still want to see it, you can [18]get your puzzle input.
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You can also [Shareon [19]Twitter [20]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/2023/about
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3. https://adventofcode.com/2023/events
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4. https://teespring.com/stores/advent-of-code
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5. https://adventofcode.com/2023/settings
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6. https://adventofcode.com/2023/auth/logout
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7. Advent of Code Supporter
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https://adventofcode.com/2023/support
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8. https://adventofcode.com/2023
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9. https://adventofcode.com/2023
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10. https://adventofcode.com/2023/support
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11. https://adventofcode.com/2023/sponsors
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12. https://adventofcode.com/2023/leaderboard
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13. https://adventofcode.com/2023/stats
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14. https://adventofcode.com/2023/sponsors
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16. https://en.wikipedia.org/wiki/Kerning
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17. https://adventofcode.com/2023
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18. https://adventofcode.com/2023/day/6/input
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