day08.js

const fs = require('fs').promises;

(async () => {
  console.log(`Reading input from ${__dirname}/${process.argv[2]}.txt`);
  const inputData = await fs.readFile(`${__dirname}/${process.argv[2]}.txt`);
  const inputs = inputData
    .toString()
    .split('\n')
    .filter((n) => n);

  let acc = 0;
  let index = 0;
  const visitedIndexs = new Set();
  while (true) {
    if (visitedIndexs.has(index)) {
      console.log('acc', acc);
      break;
    }
    visitedIndexs.add(index);
    const line = inputs[index];
    const [inc, value] = line.split(' ');

    switch (inc) {
      case 'nop': {
        index++;
        break;
      }
      case 'jmp': {
        index += parseInt(value, 10);
        break;
      }
      case 'acc': {
        index++;

        acc += parseInt(value, 10);

        break;
      }
    }
  }

  console.log('---');

  for (let changeIndex = 0; changeIndex < inputs.length; changeIndex++) {
    const puzzleInput = [...inputs];
    if (puzzleInput[changeIndex].includes('nop')) {
      puzzleInput[changeIndex] = puzzleInput[changeIndex].replace('nop', 'jmp');
    } else if (puzzleInput[changeIndex].includes('jmp')) {
      puzzleInput[changeIndex] = puzzleInput[changeIndex].replace('jmp', 'nop');
    } else {
      continue;
    }

    let acc2 = 0;
    let index2 = 0;
    const visitedIndexs2 = new Set();

    while (true) {
      if (visitedIndexs2.has(index2)) {
        break;
      }
      if (index2 >= puzzleInput.length) {
        console.log(
          'Winning change index',
          changeIndex,
          'out of',
          inputs.length
        );
        console.log('acc2', acc2);
        return;
      }
      visitedIndexs2.add(index2);
      const line = puzzleInput[index2];
      const [inc, value] = line.split(' ');

      switch (inc) {
        case 'nop': {
          index2++;
          break;
        }
        case 'jmp': {
          index2 += parseInt(value, 10);
          break;
        }
        case 'acc': {
          index2++;
          acc2 += parseInt(value, 10);
          break;
        }
      }
    }
  }
})();