216 lines
8.9 KiB
Plaintext
216 lines
8.9 KiB
Plaintext
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Advent of Code
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--- Day 21: Keypad Conundrum ---
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As you teleport onto Santa's [16]Reindeer-class starship, The Historians
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begin to panic: someone from their search party is missing. A quick
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life-form scan by the ship's computer reveals that when the missing
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Historian teleported, he arrived in another part of the ship.
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The door to that area is locked, but the computer can't open it; it can
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only be opened by physically typing the door codes (your puzzle input) on
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the numeric keypad on the door.
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The numeric keypad has four rows of buttons: 789, 456, 123, and finally an
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empty gap followed by 0A. Visually, they are arranged like this:
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+---+---+---+
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| 7 | 8 | 9 |
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+---+---+---+
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| 4 | 5 | 6 |
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+---+---+---+
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| 1 | 2 | 3 |
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+---+---+---+
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| 0 | A |
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+---+---+
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Unfortunately, the area outside the door is currently depressurized and
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nobody can go near the door. A robot needs to be sent instead.
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The robot has no problem navigating the ship and finding the numeric
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keypad, but it's not designed for button pushing: it can't be told to push
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a specific button directly. Instead, it has a robotic arm that can be
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controlled remotely via a directional keypad.
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The directional keypad has two rows of buttons: a gap / ^ (up) / A
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(activate) on the first row and < (left) / v (down) / > (right) on the
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second row. Visually, they are arranged like this:
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+---+---+
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| ^ | A |
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+---+---+---+
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| < | v | > |
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+---+---+---+
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When the robot arrives at the numeric keypad, its robotic arm is pointed
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at the A button in the bottom right corner. After that, this directional
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keypad remote control must be used to maneuver the robotic arm: the up /
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down / left / right buttons cause it to move its arm one button in that
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direction, and the A button causes the robot to briefly move forward,
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pressing the button being aimed at by the robotic arm.
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For example, to make the robot type 029A on the numeric keypad, one
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sequence of inputs on the directional keypad you could use is:
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• < to move the arm from A (its initial position) to 0.
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• A to push the 0 button.
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• ^A to move the arm to the 2 button and push it.
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• >^^A to move the arm to the 9 button and push it.
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• vvvA to move the arm to the A button and push it.
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In total, there are three shortest possible sequences of button presses on
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this directional keypad that would cause the robot to type 029A:
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<A^A>^^AvvvA, <A^A^>^AvvvA, and <A^A^^>AvvvA.
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Unfortunately, the area containing this directional keypad remote control
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is currently experiencing high levels of radiation and nobody can go near
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it. A robot needs to be sent instead.
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When the robot arrives at the directional keypad, its robot arm is pointed
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at the A button in the upper right corner. After that, a second, different
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directional keypad remote control is used to control this robot (in the
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same way as the first robot, except that this one is typing on a
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directional keypad instead of a numeric keypad).
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There are multiple shortest possible sequences of directional keypad
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button presses that would cause this robot to tell the first robot to type
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029A on the door. One such sequence is v<<A>>^A<A>AvA<^AA>A<vAAA>^A.
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Unfortunately, the area containing this second directional keypad remote
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control is currently -40 degrees! Another robot will need to be sent to
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type on that directional keypad, too.
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There are many shortest possible sequences of directional keypad button
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presses that would cause this robot to tell the second robot to tell the
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first robot to eventually type 029A on the door. One such sequence is
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<vA<AA>>^AvAA<^A>A<v<A>>^AvA^A<vA>^A<v<A>^A>AAvA^A<v<A>A>^AAAvA<^A>A.
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Unfortunately, the area containing this third directional keypad remote
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control is currently full of Historians, so no robots can find a clear
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path there. Instead, you will have to type this sequence yourself.
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Were you to choose this sequence of button presses, here are all of the
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buttons that would be pressed on your directional keypad, the two robots'
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directional keypads, and the numeric keypad:
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<vA<AA>>^AvAA<^A>A<v<A>>^AvA^A<vA>^A<v<A>^A>AAvA^A<v<A>A>^AAAvA<^A>A
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v<<A>>^A<A>AvA<^AA>A<vAAA>^A
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<A^A>^^AvvvA
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029A
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In summary, there are the following keypads:
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• One directional keypad that you are using.
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• Two directional keypads that robots are using.
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• One numeric keypad (on a door) that a robot is using.
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It is important to remember that these robots are not designed for button
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pushing. In particular, if a robot arm is ever aimed at a gap where no
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button is present on the keypad, even for an instant, the robot will panic
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unrecoverably. So, don't do that. All robots will initially aim at the
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keypad's A key, wherever it is.
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To unlock the door, five codes will need to be typed on its numeric
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keypad. For example:
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029A
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980A
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179A
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456A
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379A
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For each of these, here is a shortest sequence of button presses you could
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type to cause the desired code to be typed on the numeric keypad:
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029A: <vA<AA>>^AvAA<^A>A<v<A>>^AvA^A<vA>^A<v<A>^A>AAvA^A<v<A>A>^AAAvA<^A>A
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980A: <v<A>>^AAAvA^A<vA<AA>>^AvAA<^A>A<v<A>A>^AAAvA<^A>A<vA>^A<A>A
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179A: <v<A>>^A<vA<A>>^AAvAA<^A>A<v<A>>^AAvA^A<vA>^AA<A>A<v<A>A>^AAAvA<^A>A
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456A: <v<A>>^AA<vA<A>>^AAvAA<^A>A<vA>^A<A>A<vA>^A<A>A<v<A>A>^AAvA<^A>A
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379A: <v<A>>^AvA^A<vA<AA>>^AAvA<^A>AAvA^A<vA>^AA<A>A<v<A>A>^AAAvA<^A>A
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The Historians are getting nervous; the ship computer doesn't remember
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whether the missing Historian is trapped in the area containing a giant
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electromagnet or molten lava. You'll need to make sure that for each of
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the five codes, you find the shortest sequence of button presses
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necessary.
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The complexity of a single code (like 029A) is equal to the result of
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multiplying these two values:
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• The length of the shortest sequence of button presses you need to type
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on your directional keypad in order to cause the code to be typed on
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the numeric keypad; for 029A, this would be 68.
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• The numeric part of the code (ignoring leading zeroes); for 029A, this
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would be 29.
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In the above example, complexity of the five codes can be found by
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calculating 68 * 29, 60 * 980, 68 * 179, 64 * 456, and 64 * 379. Adding
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these together produces 126384.
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Find the fewest number of button presses you'll need to perform in order
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to cause the robot in front of the door to type each code. What is the sum
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of the complexities of the five codes on your list?
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Your puzzle answer was 248684.
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--- Part Two ---
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Just as the missing Historian is released, The Historians realize that a
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second member of their search party has also been missing this entire
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time!
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A quick life-form scan reveals the Historian is also trapped in a locked
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area of the ship. Due to a variety of hazards, robots are once again
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dispatched, forming another chain of remote control keypads managing
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robotic-arm-wielding robots.
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This time, many more robots are involved. In summary, there are the
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following keypads:
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• One directional keypad that you are using.
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• 25 directional keypads that robots are using.
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• One numeric keypad (on a door) that a robot is using.
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The keypads form a chain, just like before: your directional keypad
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controls a robot which is typing on a directional keypad which controls a
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robot which is typing on a directional keypad... and so on, ending with
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the robot which is typing on the numeric keypad.
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The door codes are the same this time around; only the number of robots
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and directional keypads has changed.
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Find the fewest number of button presses you'll need to perform in order
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to cause the robot in front of the door to type each code. What is the sum
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of the complexities of the five codes on your list?
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Your puzzle answer was 307055584161760.
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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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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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16. https://adventofcode.com/2019/day/25
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17. https://adventofcode.com/2024
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18. https://adventofcode.com/2024/day/21/input
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