balanced-parentheses.mjs

function* parenthesesPermutations_(prefix, nOpen, nClose, score) {
  if (score < 0) {
    return;
  }

  if (nOpen === 0 && nClose === 0) {
    if (score === 0) {
      yield prefix;
    }
    return;
  }

  if (nOpen > 0) {
    yield* parenthesesPermutations_(prefix + '(', nOpen - 1, nClose, score + 1);
  }

  if (nClose > 0) {
    yield* parenthesesPermutations_(prefix + ')', nOpen, nClose - 1, score - 1);
  }
}

function* parenthesesPermutations(n) {
  return yield* parenthesesPermutations_('', n, n, 0)
}

async function main() {
  const batchSize = 100;
  let batch = [];
  for (const p of parenthesesPermutations(12)) {
    if (batch.length < batchSize) {
      batch.push(p);
    } else {
      console.log(batch.join('\n'));
      batch = [];
    }
  }
  if (batch.length > 0) {
    console.log(batch.join('\n'));
  }
}

main()