this post was submitted on 06 Dec 2025
27 points (100.0% liked)

Advent Of Code

1199 readers
3 users here now

An unofficial home for the advent of code community on programming.dev! Other challenges are also welcome!

Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.

Everybody Codes is another collection of programming puzzles with seasonal events.

EC 2025

AoC 2025

Solution Threads

M T W T F S S
1 2 3 4 5 6 7
8 9 10 11 12

Visualisations Megathread

Rules/Guidelines

Relevant Communities

Relevant Links

Credits

Icon base by Lorc under CC BY 3.0 with modifications to add a gradient

console.log('Hello World')

founded 2 years ago
MODERATORS
 

Day 6: Trash Compactor

Megathread guidelines

  • Keep top level comments as only solutions, if you want to say something other than a solution put it in a new post. (replies to comments can be whatever)
  • You can send code in code blocks by using three backticks, the code, and then three backticks or use something such as https://topaz.github.io/paste/ if you prefer sending it through a URL

FAQ

you are viewing a single comment's thread
view the rest of the comments
[โ€“] Jayjader@jlai.lu 2 points 1 week ago

(Browser-based) Javascript

I got lazy and lucky writing the first part; hard-coded the number of lines / operands and it worked on the first try! I didn't factor in the final block not being padded by spaces on both sides for part 2, and so needed to test on the example code โ€“ which has 3 lines of operands instead of the problem input's 4 lines, so I had to properly solve the problem across all possible amounts of lines of input ๐Ÿ˜ฉ.

I am very jealous of all y'all who have a transpose function available in your language of choice.

Code

function part1(inputText) {
  const [firstArgs, secondArgs, thirdArgs, fourthArgs, operators] = inputText.trim().split('\n').map(line => line.trim().split(/\s+/));
  let totalSum = 0;
  for (let i = 0; i < firstArgs.length; i++) {
    if (operators[i] === '+') {
      totalSum += Number.parseInt(firstArgs[i], 10) + Number.parseInt(secondArgs[i], 10) + Number.parseInt(thirdArgs[i], 10) + Number.parseInt(fourthArgs[i], 10);
    } else if (operators[i] === '*') {
      totalSum += Number.parseInt(firstArgs[i], 10) * Number.parseInt(secondArgs[i], 10) * Number.parseInt(thirdArgs[i], 10) * Number.parseInt(fourthArgs[i], 10);
    }
  }
  return totalSum
}

{
  const start = performance.now();
  const result = part1(document.body.textContent);
  const end = performance.now();
  console.info({
    day: 6,
    part: 1,
    time: end - start,
    result
  })
}

function part2(inputText) {
  const lines = inputText.trimEnd().split('\n');
  const interBlockIndices = [];
  for (let i = 0; i < lines[0].length; i++) {
    let allEmpty = true;
    for (let j = 0; j < lines.length; j++) {
      if (lines[j][i] !== ' ') {
        allEmpty = false;
        break;
      }
    }
    if (allEmpty) {
      interBlockIndices.push(i);
    }
  }
  interBlockIndices.push(lines[0].length);

  let totalSum = 0;
  let blockStart = 0;
  for (const interBlockIndex of interBlockIndices) {
    // compute calculation of block [blockStart, interBlockIndex - 1]
    const operands = [];
    for (let i = interBlockIndex - 1; i >= blockStart; i--) {
      // parse operands
      let operand = 0;
      for (let j = 0; j < lines.length - 1; j++) {
        if (lines[j][i] !== ' ') {
          operand *= 10;
          operand += Number.parseInt(lines[j][i], 10);
        }
      }
      operands.push(operand)
    }
    if (lines.at(-1)[blockStart] === '+') {
      totalSum += operands.reduce((accu, next) => accu + next, 0);
    } else if (lines.at(-1)[blockStart] === '*') {
      totalSum += operands.reduce((accu, next) => accu * next, 1);
    }
    //  console.debug({ totalSum, operands, blockStart, interBlockIndex });
    blockStart = interBlockIndex + 1;
  }
  return totalSum;
}

{
  const example = `123 328  51 64 
 45 64  387 23 
  6 98  215 314
*   +   *   +  
`;
  const start = performance.now();
  const result = part2(document.body.textContent);
  //   const result = part2(example);
  const end = performance.now();
  console.info({
    day: 6,
    part: 2,
    time: end - start,
    result
  })
}