Day 10: Cathode-Ray Tube

There's some sort of signal defining commands to execute that add and subtract values. In Part I we multiply the value at certain cycles. In Part II we use the value as the position of a sprite and create an imag out of it.

full description

Journal

I don't remember this being too tough. Mostly just understanding what it was asking. I think there was some figuring out what the "sprite in the 3 pixels" thing was all about.

After understanding what was going on it was pretty straight forward.

It was cool to have an actual output that wasn't just a number though.

Relevant Code

const TARGET_CYCLES = [220, 180, 140, 100, 60, 20];

export const getSignalStrengths = (signal: string) => {
  const commands = signal.split("\n");

  let sum = 0;
  let cycle = 0;
  let x = 1;
  let currentCycleTarget = TARGET_CYCLES.pop();
  commands.forEach((command) => {
    let addVal = 0;
    if (command === "noop") {
      cycle++;
    } else {
      cycle += 2;
      const [_, val] = command.split(" ");
      addVal = +val;
    }
    if (cycle >= (currentCycleTarget ?? 0)) {
      sum += (currentCycleTarget ?? 0) * x;
      currentCycleTarget = TARGET_CYCLES.pop();
    }
    x += addVal;
  });

  return sum;
};

export const getScreenContent = (signal: string) => {
  const commands = signal.split("\n");

  let output = "";
  let currentCommand = commands.shift();
  let currentState = "addx";
  let spritePosition = 1;
  for (let cycle = 1; cycle < 240; cycle++) {
    const position = (cycle - 1) % 40;
    output +=
      spritePosition - 1 <= position && position <= spritePosition + 1
        ? "#"
        : ".";
    if (cycle % 40 === 0) {
      output += "\n";
    }
    if (currentCommand === "noop") {
      currentCommand = commands.shift();
    } else if (currentState === "addx") {
      currentState = "addx2";
    } else {
      const [_, val] = currentCommand!.split(" ");
      spritePosition += +val;
      currentState = "addx";
      currentCommand = commands.shift();
    }
  }

  return output;
};

Output

Test Signal

Part I: 13140 is an arbitrary value that represents "signal strength" (5 ms)

Part II:

##..##..##..##..##..##..##..##..##..##..
###...###...###...###...###...###...###.
####....####....####....####....####....
#####.....#####.....#####.....#####.....
######......######......######......####
#######.......#######.......#######....

0 ms)

Real Signal

Part I: 12640 is an arbitrary value that represents "signal strength" (0 ms)

Part II:

####.#..#.###..####.#....###....##.###..
#....#..#.#..#....#.#....#..#....#.#..#.
###..####.###....#..#....#..#....#.#..#.
#....#..#.#..#..#...#....###.....#.###..
#....#..#.#..#.#....#....#.#..#..#.#.#..
####.#..#.###..####.####.#..#..##..#..#

(0 ms)

Advent of Code 2022

Day 01 - Calorie Counting

Day 07 - No Space On Device

Day 08 - Treetop Tree House

Day 09 - Rope Bridge