jq -R -rn -f ./3-b.jq ./3.input

aoc-2025-day3-b.jq

def findLargest($n):
  . as $_ |

  .[0:(if $n == 1 then length else 1-$n end)] | max as $max |
  $_ | index($max) as $index |
  if ($n - 1) > 0 then
    [$max] + ($_[$index+1:] | findLargest($n-1))
  else
    [$max]
  end
;

[inputs | split("") | map(tonumber) | findLargest(12) | join("") | tonumber] | add

This is the code translated to JS:

import { readFile } from 'fs/promises';

function findLargest(n) {
  return (_) => {
    const max = Math.max(..._.slice(0, n == 1 ? _.length : 1 - n));
    const trimmed = _.slice(_.indexOf(max) + 1);

    if (n - 1) {
      return [max].concat(findLargest(n - 1)(trimmed));
    } else {
      return [max];
    }
  };
}

const input = (await readFile('./3.sample', 'utf8'))
  .split('\n')
  .map((line) => line.trim().split('').map(Number))
  .map(findLargest(12))
  .map((_) => parseInt(_.join(''), 10));

console.log(input.reduce((a, b) => a + b, 0));