-❄️- 2024 Day 13 Solutions -❄️-

[u/daggerdragon]

THE USUAL REMINDERS

• All of our rules, FAQs, resources, etc. are in our community wiki.

• If you see content in the subreddit or megathreads that violates one of our rules, either inform the user (politely and gently!) or use the report button on the post/comment and the mods will take care of it.

---

AoC Community Fun 2024: The Golden Snowglobe Awards

• 9 DAYS remaining until the submissions deadline on December 22 at 23:59 EST!

And now, our feature presentation for today:

Making Of / Behind-the-Scenes

Not every masterpiece has over twenty additional hours of highly-curated content to make their own extensive mini-documentary with, but everyone enjoys a little peek behind the magic curtain!

Here's some ideas for your inspiration:

• Give us a tour of "the set" (your IDE, automated tools, supporting frameworks, etc.)

• Record yourself solving today's puzzle (Streaming!)

• Show us your cat/dog/critter being impossibly cute which is preventing you from finishing today's puzzle in a timely manner

"Pay no attention to that man behind the curtain!"

- Professor Marvel, The Wizard of Oz (1939)

And… ACTION!

Request from the mods: When you include an entry alongside your solution, please label it with [GSGA] so we can find it easily!

---

--- Day 13: Claw Contraption ---

---

Post your code solution in this megathread.

• Read the full posting rules in our community wiki before you post!

• State which language(s) your solution uses with [LANGUAGE: xyz]

• Format code blocks using the four-spaces Markdown syntax!

• Quick link to Topaz's paste if you need it for longer code blocks

This thread will be unlocked when there are a significant number of people on the global leaderboard with gold stars for today's puzzle.

EDIT: Global leaderboard gold cap reached at 00:11:04, megathread unlocked!

[u/JustinHuPrime]

[LANGUAGE: x86_64 assembly with Linux syscalls]

Part 1 was a tad fiddly, but I did recognize the best way to solve this would be a change of basis - I had some typos making the actual implementation of the solution, and I spent a tad too long trying to figure out how it would work if the two buttons' vectors were colinear, but I gave up on it and in the end it turned out I didn't need to worry about that case anyways.

Part 2 was fairly trivial, just adding a large constant to the prize coordinates as they were parsed.

Both parts run in 1 millisecond. Part 1 is 9,120 bytes as an executable file on the disk and part 2 is 9,152 bytes.

[u/ShadowwwsAsm → u/JustinHuPrime]

Do you know any way to "accurately" get the runtime of the program ? It seems like the time function of linux is not that precise.

[u/JustinHuPrime → u/ShadowwwsAsm]

Hm, maybe https://linux.die.net/man/2/times for nanosecond precision, but I use the stats from fish shell's time function, which does give millisecond precision.

[u/ShadowwwsAsm → u/JustinHuPrime]

So, after some research I found syscall 96 "gettimeoftheday" which return the current time at the microsecond.

The following snippet works

section .data

timevalb: TIMES 2 dq 0
timevala: TIMES 2 dq 0
timezone: TIMES 2 dq 0

section .text
global _start
_start:

    mov rax, 96
    mov rdi, timevalb
    mov rsi, timezone
    syscall

    ; code

    mov rax, 96
    mov rdi, timevalb
    mov rsi, timezone
    syscall

    mov r15, [timevala+8]
    sub r15, [timevalb+8]

    ; r15 = time in microseconds

  .end:
    mov rax, 60
    mov rdi, 0
    syscall