122 lines
4.6 KiB
Plaintext
122 lines
4.6 KiB
Plaintext
Advent of Code
|
||
|
||
--- Day 11: Chronal Charge ---
|
||
|
||
You watch the Elves and their sleigh fade into the distance as they head
|
||
toward the North Pole.
|
||
|
||
Actually, you're the one fading. The falling sensation returns.
|
||
|
||
The low fuel warning light is illuminated on your wrist-mounted device.
|
||
Tapping it once causes it to project a hologram of the situation: a 300x300
|
||
grid of fuel cells and their current power levels, some negative. You're not
|
||
sure what negative power means in the context of time travel, but it can't
|
||
be good.
|
||
|
||
Each fuel cell has a coordinate ranging from 1 to 300 in both the X
|
||
(horizontal) and Y (vertical) direction. In X,Y notation, the top-left cell
|
||
is 1,1, and the top-right cell is 300,1.
|
||
|
||
The interface lets you select any 3x3 square of fuel cells. To increase your
|
||
chances of getting to your destination, you decide to choose the 3x3 square
|
||
with the largest total power.
|
||
|
||
The power level in a given fuel cell can be found through the following
|
||
process:
|
||
|
||
* Find the fuel cell's rack ID, which is its X coordinate plus 10. * Begin
|
||
with a power level of the rack ID times the Y coordinate. * Increase the
|
||
power level by the value of the grid serial number (your puzzle input).
|
||
* Set the power level to itself multiplied by the rack ID. * Keep only the
|
||
hundreds digit of the power level (so 12345 becomes 3; numbers with no
|
||
hundreds digit become 0). * Subtract 5 from the power level.
|
||
|
||
For example, to find the power level of the fuel cell at 3,5 in a grid with
|
||
serial number 8:
|
||
|
||
* The rack ID is 3 + 10 = 13. * The power level starts at 13 * 5 = 65.
|
||
* Adding the serial number produces 65 + 8 = 73. * Multiplying by the rack
|
||
ID produces 73 * 13 = 949. * The hundreds digit of 949 is 9. * Subtracting
|
||
5 produces 9 - 5 = 4.
|
||
|
||
So, the power level of this fuel cell is 4.
|
||
|
||
Here are some more example power levels:
|
||
|
||
* Fuel cell at 122,79, grid serial number 57: power level -5. * Fuel cell
|
||
at 217,196, grid serial number 39: power level 0. * Fuel cell at 101,153,
|
||
grid serial number 71: power level 4.
|
||
|
||
Your goal is to find the 3x3 square which has the largest total power. The
|
||
square must be entirely within the 300x300 grid. Identify this square using
|
||
the X,Y coordinate of its top-left fuel cell. For example:
|
||
|
||
For grid serial number 18, the largest total 3x3 square has a top-left
|
||
corner of 33,45 (with a total power of 29); these fuel cells appear in the
|
||
middle of this 5x5 region:
|
||
|
||
-2 -4 4 4 4
|
||
-4 4 4 4 -5
|
||
4 3 3 4 -4
|
||
1 1 2 4 -3
|
||
-1 0 2 -5 -2
|
||
|
||
For grid serial number 42, the largest 3x3 square's top-left is 21,61 (with
|
||
a total power of 30); they are in the middle of this region:
|
||
|
||
-3 4 2 2 2
|
||
-4 4 3 3 4
|
||
-5 3 3 4 -4
|
||
4 3 3 4 -3
|
||
3 3 3 -5 -1
|
||
|
||
What is the X,Y coordinate of the top-left fuel cell of the 3x3 square with
|
||
the largest total power?
|
||
|
||
Your puzzle answer was 243,49.
|
||
|
||
--- Part Two ---
|
||
|
||
You discover a dial on the side of the device; it seems to let you select a
|
||
square of any size, not just 3x3. Sizes from 1x1 to 300x300 are supported.
|
||
|
||
Realizing this, you now must find the square of any size with the largest
|
||
total power. Identify this square by including its size as a third parameter
|
||
after the top-left coordinate: a 9x9 square with a top-left corner of 3,5 is
|
||
identified as 3,5,9.
|
||
|
||
For example:
|
||
|
||
* For grid serial number 18, the largest total square (with a total power
|
||
of 113) is 16x16 and has a top-left corner of 90,269, so its identifier is
|
||
90,269,16. * For grid serial number 42, the largest total square (with a
|
||
total power of 119) is 12x12 and has a top-left corner of 232,251, so its
|
||
identifier is 232,251,12.
|
||
|
||
What is the X,Y,size identifier of the square with the largest total power?
|
||
|
||
Your puzzle answer was 285,169,15.
|
||
|
||
Both parts of this puzzle are complete! They provide two gold stars: **
|
||
|
||
Your puzzle input was 5093.
|
||
|
||
References
|
||
|
||
Visible links
|
||
. https://adventofcode.com/
|
||
. https://adventofcode.com/2018/about
|
||
. https://adventofcode.com/2018/events
|
||
. https://adventofcode.com/2018/settings
|
||
. https://adventofcode.com/2018/auth/logout
|
||
. Advent of Code Supporter
|
||
https://adventofcode.com/2018/support
|
||
. https://adventofcode.com/2018
|
||
. https://adventofcode.com/2018
|
||
. https://adventofcode.com/2018/support
|
||
. https://adventofcode.com/2018/sponsors
|
||
. https://adventofcode.com/2018/leaderboard
|
||
. https://adventofcode.com/2018/stats
|
||
. https://adventofcode.com/2018/sponsors
|
||
. https://adventofcode.com/2018
|