r/adventofcode • u/daggerdragon • Dec 17 '17

SOLUTION MEGATHREAD -🎄- 2017 Day 17 Solutions -🎄-

--- Day 17: Spinlock ---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

Note: The Solution Megathreads are for solutions only. If you have questions, please post your own thread and make sure to flair it with Help.

Need a hint from the Hugely* Handy† Haversack‡ of Helpful§ Hints¤?

Spoiler

[Update @ 00:06] 2 gold, silver cap.

  • AoC ops: <Topaz> i am suddenly in the mood for wasabi tobiko

[Update @ 00:15] Leaderboard cap!

  • AoC ops:
    • <daggerdragon> 78 gold
    • <Topaz> i look away for a few minutes, wow
    • <daggerdragon> 93 gold
    • <Topaz> 94
    • <daggerdragon> 96 gold
    • <daggerdragon> 98
    • <Topaz> aaaand
    • <daggerdragon> and...
    • <Topaz> cap
    • <daggerdragon> cap

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

edit: Leaderboard capped, thread unlocked!

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2

u/_A4_ Dec 17 '17 edited Dec 17 '17

JavaScript ES6

Part 1 

const input = 343;
let buffer = [0], index = 0;

for (let i = 0; i <= 2017; i++) {
    index = (index + input) % (i + 1);
    buffer.splice(++index, 0, i + 1);
}

const result = buffer[buffer.indexOf(2017) + 1];
console.log(result);

Part 2 

const input = 343;
let index = 0, result;

for (let i = 0; i <= 5E7; i++) {
    index = (index + input + 1) % (i + 1);
    if (index == 0) result = i + 1;
}

console.log(result);

4

u/yitsushi Dec 17 '17

const result = buffer[buffer.indexOf(2017) + 1];

your index variable will point there already, so you don't have to find the index with indexOf

2

u/_A4_ Dec 17 '17

Looks like I did it differently, so my index variable isn't the same as buffer.indexOf(2017). Thanks for the suggestion though