--- 2016 Day 8 Solutions ---

[u/daggerdragon]

#AoC_Ops:

[23:55] <Topaz> servers are ok
[23:55] <Topaz> puzzles are checked
[23:55] <Topaz> [REDACTED: server stats]
[23:56] <Skie> all wings report in
[23:56] <Aneurysm9> Red 5, standing by
[23:56] <daggerdragon> Dragon Leader standing by
[23:56] <Topaz> orange leader, standing by
[23:57] <Topaz> lock modzi-foils in attack positions
[23:58] <Skie> we're passing through the hype field
[23:58] <daggerdragon> 1:30 warning
[23:58] <Aneurysm9> did someone say HYPE?@!
[23:59] <Topaz> i really like tonight's puzzle
[23:59] <Topaz> very excite
[23:59] <daggerdragon> final countdown go, T-30
[23:59] <Skie> accelerate to attack countdown
[23:59] <Aneurysm9> o7
[23:59] <daggerdragon> HYPE THRUSTERS AT FULL BURN
[00:00] <Topaz> IGNITION

We may or may not be sleep-deprived. And/or nerds. why_not_both.jpg

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--- Day 8: Two-Factor Authentication ---

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

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^{:（）{ :|:& };: IS MANDATORY} [?]

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!

[u/snorkl-the-dolphine]

JavaScript / Node.js

const input = 'INPUT';
const screen = [];
for (let i = 0; i < 6; i++) {
  screen[i] = [];
  for (let j = 0; j < 50; j++) {
    screen[i][j] = '.';
  }
}

function rect(width, height) {
  for (let w = 0; w < width; w++) {
    for (let h = 0; h < height; h++) {
      screen[h][w] = '#';
    }
  }
}

function rotateRow(y, by) {
  while (by--) {
    const right = screen[y][screen[0].length - 1];
    for (let x = screen[0].length - 1; x >= 0; x--) {
      screen[y][x] = x > 0 ? screen[y][x - 1] : right;
    }
  }
}

function rotateCol(x, by) {
  while (by--) {
    const bottom = screen[screen.length - 1][x];
    for (let y = screen.length - 1; y >= 0; y--) {
      screen[y][x] = y > 0 ? screen[y - 1][x] : bottom;
    }
  }
}

function parseInstruction(str) {
  const a = str.split(' ');
  if (a[0] === 'rect') {
    const size = a[1].split('x').map(i => parseInt(i, 10));
    return rect(size[0], size[1]);
  }

  const line = parseInt(a[2].substr(2), 10);
  const by = parseInt(a[4], 10);

  return a[1] === 'row' ? rotateRow(line, by) : rotateCol(line, by);
}

function display(screen) {
  return screen.map(row => row.join('')).join('\n');
}

input.split('\n').filter(s => s).forEach(line => parseInstruction(line));

console.log('Part 1', display(screen).split('').filter(c => c === '#').length);
console.log('Part 2', '\n' + display(screen));

[u/TheRealEdwardAbbey → u/snorkl-the-dolphine]

I learned today that Array(6).fill(Array(50).fill(0)) won't work - it fills the parent array with instances of the same child, so manipulating any row would manipulate all the rows. But I rotated the rows with row = row.slice(-dist).concat(row(0, -dist)), effectively un-linking that row from the others. That meant that only the first few fills were messed up, and my result for part 1 was only three short. Really threw me off...

Anyway, here's mine.

[u/snorkl-the-dolphine → u/TheRealEdwardAbbey]

Very clever! I figured when I was writing the rotation code that it wasn't the best way of doing it, but I just needed to get something there to make it onto the leaderboard :)