Advent-of-Code/2021/22/README.md

# 2021 Day 22: Reactor Reboot
Copyright (c) Eric Wastl
#### [Direct Link](https://adventofcode.com/2021/day/22)

## Part 1

Operating at these extreme ocean depths has overloaded the submarine's reactor; it needs to be rebooted.

The reactor core is made up of a large 3-dimensional grid made up entirely of cubes, one cube per integer 3-dimensional coordinate (`x,y,z`). Each cube can be either **on** or **off**; at the start of the reboot process, they are all **off**. (Could it be an old model of a reactor you've seen [before](https://adventofcode.com/2020/day/17)?)

To reboot the reactor, you just need to set all of the cubes to either **on** or **off** by following a list of **reboot steps** (your puzzle input). Each step specifies a [cuboid](https://en.wikipedia.org/wiki/Cuboid) (the set of all cubes that have coordinates which fall within ranges for `x`, `y`, and `z`) and whether to turn all of the cubes in that cuboid **on** or **off**.

For example, given these reboot steps:

```
on x=10..12,y=10..12,z=10..12
on x=11..13,y=11..13,z=11..13
off x=9..11,y=9..11,z=9..11
on x=10..10,y=10..10,z=10..10
```

The first step (`on x=10..12,y=10..12,z=10..12`) turns **on** a 3x3x3 cuboid consisting of 27 cubes:

- `10,10,10`
- `10,10,11`
- `10,10,12`
- `10,11,10`
- `10,11,11`
- `10,11,12`
- `10,12,10`
- `10,12,11`
- `10,12,12`
- `11,10,10`
- `11,10,11`
- `11,10,12`
- `11,11,10`
- `11,11,11`
- `11,11,12`
- `11,12,10`
- `11,12,11`
- `11,12,12`
- `12,10,10`
- `12,10,11`
- `12,10,12`
- `12,11,10`
- `12,11,11`
- `12,11,12`
- `12,12,10`
- `12,12,11`
- `12,12,12`

The second step (`on x=11..13,y=11..13,z=11..13`) turns **on** a 3x3x3 cuboid that overlaps with the first. As a result, only 19 additional cubes turn on; the rest are already on from the previous step:

- `11,11,13`
- `11,12,13`
- `11,13,11`
- `11,13,12`
- `11,13,13`
- `12,11,13`
- `12,12,13`
- `12,13,11`
- `12,13,12`
- `12,13,13`
- `13,11,11`
- `13,11,12`
- `13,11,13`
- `13,12,11`
- `13,12,12`
- `13,12,13`
- `13,13,11`
- `13,13,12`
- `13,13,13`

The third step (`off x=9..11,y=9..11,z=9..11`) turns **off** a 3x3x3 cuboid that overlaps partially with some cubes that are on, ultimately turning off 8 cubes:

- `10,10,10`
- `10,10,11`
- `10,11,10`
- `10,11,11`
- `11,10,10`
- `11,10,11`
- `11,11,10`
- `11,11,11`

The final step (`on x=10..10,y=10..10,z=10..10`) turns **on** a single cube, `10,10,10`. After this last step, **`39`** cubes are **on**.

The initialization procedure only uses cubes that have x, y, and z positions of at least `-50` and at most `50`. For now, ignore cubes outside this region.

Here is a larger example:

```
on x=-20..26,y=-36..17,z=-47..7
on x=-20..33,y=-21..23,z=-26..28
on x=-22..28,y=-29..23,z=-38..16
on x=-46..7,y=-6..46,z=-50..-1
on x=-49..1,y=-3..46,z=-24..28
on x=2..47,y=-22..22,z=-23..27
on x=-27..23,y=-28..26,z=-21..29
on x=-39..5,y=-6..47,z=-3..44
on x=-30..21,y=-8..43,z=-13..34
on x=-22..26,y=-27..20,z=-29..19
off x=-48..-32,y=26..41,z=-47..-37
on x=-12..35,y=6..50,z=-50..-2
off x=-48..-32,y=-32..-16,z=-15..-5
on x=-18..26,y=-33..15,z=-7..46
off x=-40..-22,y=-38..-28,z=23..41
on x=-16..35,y=-41..10,z=-47..6
off x=-32..-23,y=11..30,z=-14..3
on x=-49..-5,y=-3..45,z=-29..18
off x=18..30,y=-20..-8,z=-3..13
on x=-41..9,y=-7..43,z=-33..15
on x=-54112..-39298,y=-85059..-49293,z=-27449..7877
on x=967..23432,y=45373..81175,z=27513..53682
```

The last two steps are fully outside the initialization procedure area; all other steps are fully within it. After executing these steps in the initialization procedure region, **`590784`** cubes are **on**.

Execute the reboot steps. Afterward, considering only cubes in the region `x=-50..50,y=-50..50,z=-50..50`, how many cubes are on?

## Part 2

Now that the initialization procedure is complete, you can reboot the reactor.

Starting with all cubes **off**, run all of the **reboot steps** for all cubes in the reactor.

Consider the following reboot steps:

```
on x=-5..47,y=-31..22,z=-19..33
on x=-44..5,y=-27..21,z=-14..35
on x=-49..-1,y=-11..42,z=-10..38
on x=-20..34,y=-40..6,z=-44..1
off x=26..39,y=40..50,z=-2..11
on x=-41..5,y=-41..6,z=-36..8
off x=-43..-33,y=-45..-28,z=7..25
on x=-33..15,y=-32..19,z=-34..11
off x=35..47,y=-46..-34,z=-11..5
on x=-14..36,y=-6..44,z=-16..29
on x=-57795..-6158,y=29564..72030,z=20435..90618
on x=36731..105352,y=-21140..28532,z=16094..90401
on x=30999..107136,y=-53464..15513,z=8553..71215
on x=13528..83982,y=-99403..-27377,z=-24141..23996
on x=-72682..-12347,y=18159..111354,z=7391..80950
on x=-1060..80757,y=-65301..-20884,z=-103788..-16709
on x=-83015..-9461,y=-72160..-8347,z=-81239..-26856
on x=-52752..22273,y=-49450..9096,z=54442..119054
on x=-29982..40483,y=-108474..-28371,z=-24328..38471
on x=-4958..62750,y=40422..118853,z=-7672..65583
on x=55694..108686,y=-43367..46958,z=-26781..48729
on x=-98497..-18186,y=-63569..3412,z=1232..88485
on x=-726..56291,y=-62629..13224,z=18033..85226
on x=-110886..-34664,y=-81338..-8658,z=8914..63723
on x=-55829..24974,y=-16897..54165,z=-121762..-28058
on x=-65152..-11147,y=22489..91432,z=-58782..1780
on x=-120100..-32970,y=-46592..27473,z=-11695..61039
on x=-18631..37533,y=-124565..-50804,z=-35667..28308
on x=-57817..18248,y=49321..117703,z=5745..55881
on x=14781..98692,y=-1341..70827,z=15753..70151
on x=-34419..55919,y=-19626..40991,z=39015..114138
on x=-60785..11593,y=-56135..2999,z=-95368..-26915
on x=-32178..58085,y=17647..101866,z=-91405..-8878
on x=-53655..12091,y=50097..105568,z=-75335..-4862
on x=-111166..-40997,y=-71714..2688,z=5609..50954
on x=-16602..70118,y=-98693..-44401,z=5197..76897
on x=16383..101554,y=4615..83635,z=-44907..18747
off x=-95822..-15171,y=-19987..48940,z=10804..104439
on x=-89813..-14614,y=16069..88491,z=-3297..45228
on x=41075..99376,y=-20427..49978,z=-52012..13762
on x=-21330..50085,y=-17944..62733,z=-112280..-30197
on x=-16478..35915,y=36008..118594,z=-7885..47086
off x=-98156..-27851,y=-49952..43171,z=-99005..-8456
off x=2032..69770,y=-71013..4824,z=7471..94418
on x=43670..120875,y=-42068..12382,z=-24787..38892
off x=37514..111226,y=-45862..25743,z=-16714..54663
off x=25699..97951,y=-30668..59918,z=-15349..69697
off x=-44271..17935,y=-9516..60759,z=49131..112598
on x=-61695..-5813,y=40978..94975,z=8655..80240
off x=-101086..-9439,y=-7088..67543,z=33935..83858
off x=18020..114017,y=-48931..32606,z=21474..89843
off x=-77139..10506,y=-89994..-18797,z=-80..59318
off x=8476..79288,y=-75520..11602,z=-96624..-24783
on x=-47488..-1262,y=24338..100707,z=16292..72967
off x=-84341..13987,y=2429..92914,z=-90671..-1318
off x=-37810..49457,y=-71013..-7894,z=-105357..-13188
off x=-27365..46395,y=31009..98017,z=15428..76570
off x=-70369..-16548,y=22648..78696,z=-1892..86821
on x=-53470..21291,y=-120233..-33476,z=-44150..38147
off x=-93533..-4276,y=-16170..68771,z=-104985..-24507
```

After running the above reboot steps, **`2758514936282235`** cubes are on. (Just for fun, `474140` of those are also in the initialization procedure region.)

Starting again with all cubes **off**, execute all reboot steps. Afterward, considering all cubes, **how many cubes are on?**