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The best thing from Gouda since…

Advent of Code 2025

What’s the best thing to come out of Gouda after cheese? We like to think it’s Technolution. Just like Gouda cheese, we’re all about quality – but instead of dairy, we’re into solving puzzles. Big ones, small ones, complex ones, and sometimes even the kind that make you want to pull your hair out. Puzzling isn’t just a hobby here; it’s who we are.

We love Puzzles

At Technolution, we love puzzles. Whether it’s tackling complex technical challenges for our clients or solving the brain-teasing riddles of Advent of Code, puzzling is in our DNA. For years, our colleagues have enthusiastically (and occasionally with a bit of frustration 😉) taken part in Advent of Code.

We’re proud to sponsor Advent of Code. Because we want to make sure everyone can continue enjoying this amazing initiative!

Happy puzzling

Happy puzzling, and who knows – we might just see your name on the Advent of Code leaderboard.

Puzzle

Santa Claus has installed a heat pump and solar panels, but at the moment, the elves’ workshop is freezing cold, and upon further inspection it seems that there are serious problems in the electricity grid.

The overhead cables all seem to be fine, but the underground cables seem to be the cause of the congestion. The cables were installed back in 1987, and most of the elves who worked on the project back then are now retired. One of the elves who still works for Santa Claus has managed to find a blueprint, but unfortunately, it was stored in a format that can’t easily be parsed by the modern North Pole computers. It also seems to be somewhat incomplete.

Apparently, the electricity grid is a 2D grid of cells, and all cables are laid down only in horizontal or vertical segments. Unfortunately, the elves have used non-lightfast markers to draw the cables, and after 38 years these are no longer visible. Only the start and end positions, and some of the joints are still visible, and the architect has given you an ordered list of all these positions. There also appear to be some walls between the cells, and the architect ensures you that no cable can pass through these walls. You have also been told that resources were scarce back then, and the shortest path has always been used to route a cable. There can be only one cable per cell, though, so the shortest path may be longer than expected.

Example

GRID 4 5 . . . . . - . # # . . .|. . . . . . . . . CABLE (3,0) (0,1) (0,4) (2,1) CABLE (2,4) (3,1)

The first line specifies the grid size in rows and columns, respectively. After that follows a description of the grid, where “-” and “|” indicate the position of walls. Unused space is indicated by the “#” symbol. Electricity cables cannot use those places. The positions for each cable are specified on a separate line, starting with the word “CABLE“. Each position is specified as (row, column), starting from the top-left at (0,0). Using this information, the cable layout is uniquely defined. It may well be that your puzzle input, however, is not uniquely defined.

For each cable, add the length of the cable to the number of direction changes it makes. Multiply the values for each cable together to get your answer. In the example, cable A makes 5 turns, and has length 13. Cable B only makes 1 turn and has length 5. The answer for the example is (5+13) * (1+5) = 108.

If you have found the correct answer, you may proceed to the next part of the puzzle by visiting the following secret URL: https://www.technolution.com/career/advent-of-code-2025-NUMBER, where you replace NUMBER by your solution, e.g. https://www.technolution.com/career/advent-of-code-2025-108/.

You can download your puzzle input here.

I need a hint