(Browser-based) Javascript

For part 2, I eagerly wrote a nice, clean, generic, functional depth-first search, only to get an out of memory error 😭. Note the top-level code blocks: they scope the variables declared inside them, allowing me to run the whole script repeatedly in the console without getting “redeclared variable name” errors.

function part1(inputText) {
  let totalOutputJoltage = 0;
  for (const batteryBankDef of inputText.split('\n')) {
    let bestBankJoltage = 0;
    const previousDigits = [];
    for (const character of batteryBankDef) {
      const currentDigit = Number.parseInt(character, 10);
      for (const previousDigit of previousDigits) {
        const possibleVoltage = 10 * previousDigit + currentDigit;
        if (possibleVoltage > bestBankJoltage) {
          bestBankJoltage = possibleVoltage;
        }
      }
      previousDigits.push(currentDigit);
    }
        totalOutputJoltage += bestBankJoltage;
  }
  return totalOutputJoltage;
}
{
    const start = performance.now();
    const result = part1(document.body.textContent)
    const end = performance.now();
    console.info({day: 3, part: 1, result, time: end - start})
}

function findNthDigitForSequence(bankDef, n, startIndex) {
  let digit = 9;
  while (digit > 0) {
    for (let i = startIndex; i < bankDef.length - 11 + n; i++) {
      if (bankDef[i] === digit.toString()) {
        return [digit, i]
      }
    }
    digit--;
  }
  return undefined;
}
function findBestJoltageForBank(bankDef) {
  const digits = [];
  let previousFoundDigitIndex = -1;
  for (let i = 0; i < 12; i++) {
    const digitFound = findNthDigitForSequence(bankDef, i, previousFoundDigitIndex + 1);
    if (digitFound === undefined) {
      debugger;
      return undefined;
    }
    const [digit, index] = digitFound;
    digits.push(digit);
    previousFoundDigitIndex = index;
  }
  return Number.parseInt(digits.join(''), 10);
}
function part2(inputText) {
  let totalOutputJoltage = 0;
  for (const batteryBankDef of inputText.trim().split('\n')) {
    totalOutputJoltage += findBestJoltageForBank(batteryBankDef) ?? 0;
  }
  return totalOutputJoltage;
}

{
  const start = performance.now();
  const result = part2(document.body.textContent);
  const end = performance.now();
  console.info({ day: 3, part: 2, time: end - start, result });
}