# Day 8: Playground

[https://adventofcode.com/2025/day/8](https://adventofcode.com/2025/day/8)

## Description

### Part One

Equipped with a new understanding of teleporter maintenance, you confidently step onto the repaired teleporter pad.

You rematerialize on an unfamiliar teleporter pad and find yourself in a vast underground space which contains a giant playground!

Across the playground, a group of Elves are working on setting up an ambitious Christmas decoration project. Through careful rigging, they have suspended a large number of small electrical [junction boxes](https://en.wikipedia.org/wiki/Junction_box).

Their plan is to connect the junction boxes with long strings of lights. Most of the junction boxes don't provide electricity; however, when two junction boxes are connected by a string of lights, electricity can pass between those two junction boxes.

The Elves are trying to figure out _which junction boxes to connect_ so that electricity can reach _every_ junction box. They even have a list of all of the junction boxes' positions in 3D space (your puzzle input).

For example:

    162,817,812
    57,618,57
    906,360,560
    592,479,940
    352,342,300
    466,668,158
    542,29,236
    431,825,988
    739,650,466
    52,470,668
    216,146,977
    819,987,18
    117,168,530
    805,96,715
    346,949,466
    970,615,88
    941,993,340
    862,61,35
    984,92,344
    425,690,689
    

This list describes the position of 20 junction boxes, one per line. Each position is given as `X,Y,Z` coordinates. So, the first junction box in the list is at `X=162`, `Y=817`, `Z=812`.

To save on string lights, the Elves would like to focus on connecting pairs of junction boxes that are _as close together as possible_ according to [straight-line distance](https://en.wikipedia.org/wiki/Euclidean_distance). In this example, the two junction boxes which are closest together are `162,817,812` and `425,690,689`.

By connecting these two junction boxes together, because electricity can flow between them, they become part of the same _circuit_. After connecting them, there is a single circuit which contains two junction boxes, and the remaining 18 junction boxes remain in their own individual circuits.

Now, the two junction boxes which are closest together but aren't already directly connected are `162,817,812` and `431,825,988`. After connecting them, since `162,817,812` is already connected to another junction box, there is now a single circuit which contains _three_ junction boxes and an additional 17 circuits which contain one junction box each.

The next two junction boxes to connect are `906,360,560` and `805,96,715`. After connecting them, there is a circuit containing 3 junction boxes, a circuit containing 2 junction boxes, and 15 circuits which contain one junction box each.

The next two junction boxes are `431,825,988` and `425,690,689`. Because these two junction boxes were _already in the same circuit_, nothing happens!

This process continues for a while, and the Elves are concerned that they don't have enough extension cables for all these circuits. They would like to know how big the circuits will be.

After making the ten shortest connections, there are 11 circuits: one circuit which contains _5_ junction boxes, one circuit which contains _4_ junction boxes, two circuits which contain _2_ junction boxes each, and seven circuits which each contain a single junction box. Multiplying together the sizes of the three largest circuits (5, 4, and one of the circuits of size 2) produces _`40`_.

Your list contains many junction boxes; connect together the _1000_ pairs of junction boxes which are closest together. Afterward, _what do you get if you multiply together the sizes of the three largest circuits?_