2018-12-03 21:30:30 +00:00
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Advent of Code
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--- Day 11: Chronal Charge ---
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2019-11-08 21:01:07 +00:00
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You watch the Elves and their sleigh fade into the distance as they head
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toward the North Pole.
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2018-12-03 21:30:30 +00:00
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Actually, you're the one fading. The falling sensation returns.
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2019-11-08 21:01:07 +00:00
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The low fuel warning light is illuminated on your wrist-mounted device.
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Tapping it once causes it to project a hologram of the situation: a 300x300
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grid of fuel cells and their current power levels, some negative. You're not
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sure what negative power means in the context of time travel, but it can't
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be good.
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2018-12-03 21:30:30 +00:00
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2019-11-08 21:01:07 +00:00
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Each fuel cell has a coordinate ranging from 1 to 300 in both the X
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(horizontal) and Y (vertical) direction. In X,Y notation, the top-left cell
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is 1,1, and the top-right cell is 300,1.
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2018-12-03 21:30:30 +00:00
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2019-11-08 21:01:07 +00:00
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The interface lets you select any 3x3 square of fuel cells. To increase your
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chances of getting to your destination, you decide to choose the 3x3 square
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with the largest total power.
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2018-12-03 21:30:30 +00:00
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2019-11-08 21:01:07 +00:00
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The power level in a given fuel cell can be found through the following
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process:
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2018-12-03 21:30:30 +00:00
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2019-11-08 21:01:07 +00:00
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* Find the fuel cell's rack ID, which is its X coordinate plus 10. * Begin
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with a power level of the rack ID times the Y coordinate. * Increase the
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power level by the value of the grid serial number (your puzzle input).
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* Set the power level to itself multiplied by the rack ID. * Keep only the
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hundreds digit of the power level (so 12345 becomes 3; numbers with no
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hundreds digit become 0). * Subtract 5 from the power level.
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2018-12-03 21:30:30 +00:00
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2019-11-08 21:01:07 +00:00
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For example, to find the power level of the fuel cell at 3,5 in a grid with
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serial number 8:
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2018-12-03 21:30:30 +00:00
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2019-11-08 21:01:07 +00:00
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* The rack ID is 3 + 10 = 13. * The power level starts at 13 * 5 = 65.
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* Adding the serial number produces 65 + 8 = 73. * Multiplying by the rack
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ID produces 73 * 13 = 949. * The hundreds digit of 949 is 9. * Subtracting
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5 produces 9 - 5 = 4.
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2018-12-03 21:30:30 +00:00
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So, the power level of this fuel cell is 4.
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Here are some more example power levels:
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2019-11-08 21:01:07 +00:00
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* Fuel cell at 122,79, grid serial number 57: power level -5. * Fuel cell
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at 217,196, grid serial number 39: power level 0. * Fuel cell at 101,153,
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grid serial number 71: power level 4.
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2018-12-03 21:30:30 +00:00
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2019-11-08 21:01:07 +00:00
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Your goal is to find the 3x3 square which has the largest total power. The
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square must be entirely within the 300x300 grid. Identify this square using
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the X,Y coordinate of its top-left fuel cell. For example:
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2018-12-03 21:30:30 +00:00
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2019-11-08 21:01:07 +00:00
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For grid serial number 18, the largest total 3x3 square has a top-left
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corner of 33,45 (with a total power of 29); these fuel cells appear in the
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middle of this 5x5 region:
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2018-12-03 21:30:30 +00:00
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-2 -4 4 4 4
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-4 4 4 4 -5
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4 3 3 4 -4
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1 1 2 4 -3
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-1 0 2 -5 -2
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2019-11-08 21:01:07 +00:00
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For grid serial number 42, the largest 3x3 square's top-left is 21,61 (with
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a total power of 30); they are in the middle of this region:
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2018-12-03 21:30:30 +00:00
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-3 4 2 2 2
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-4 4 3 3 4
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-5 3 3 4 -4
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4 3 3 4 -3
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3 3 3 -5 -1
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2019-11-08 21:01:07 +00:00
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What is the X,Y coordinate of the top-left fuel cell of the 3x3 square with
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the largest total power?
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2018-12-03 21:30:30 +00:00
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Your puzzle answer was 243,49.
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--- Part Two ---
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2019-11-08 21:01:07 +00:00
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You discover a dial on the side of the device; it seems to let you select a
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square of any size, not just 3x3. Sizes from 1x1 to 300x300 are supported.
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2018-12-03 21:30:30 +00:00
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2019-11-08 21:01:07 +00:00
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Realizing this, you now must find the square of any size with the largest
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total power. Identify this square by including its size as a third parameter
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after the top-left coordinate: a 9x9 square with a top-left corner of 3,5 is
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identified as 3,5,9.
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2018-12-03 21:30:30 +00:00
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For example:
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2019-11-08 21:01:07 +00:00
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* For grid serial number 18, the largest total square (with a total power
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of 113) is 16x16 and has a top-left corner of 90,269, so its identifier is
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90,269,16. * For grid serial number 42, the largest total square (with a
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total power of 119) is 12x12 and has a top-left corner of 232,251, so its
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identifier is 232,251,12.
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2018-12-03 21:30:30 +00:00
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What is the X,Y,size identifier of the square with the largest total power?
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Your puzzle answer was 285,169,15.
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Both parts of this puzzle are complete! They provide two gold stars: **
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Your puzzle input was 5093.
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References
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Visible links
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. https://adventofcode.com/
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. https://adventofcode.com/2018/about
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. https://adventofcode.com/2018/events
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. https://adventofcode.com/2018/settings
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. https://adventofcode.com/2018/auth/logout
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. Advent of Code Supporter
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https://adventofcode.com/2018/support
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. https://adventofcode.com/2018
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. https://adventofcode.com/2018
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. https://adventofcode.com/2018/support
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. https://adventofcode.com/2018/sponsors
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. https://adventofcode.com/2018/leaderboard
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. https://adventofcode.com/2018/stats
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. https://adventofcode.com/2018/sponsors
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. https://adventofcode.com/2018
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