147 lines
6.5 KiB
Plaintext
147 lines
6.5 KiB
Plaintext
Advent of Code
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--- Day 17: Reservoir Research ---
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You arrive in the year 18. If it weren't for the coat you got in 1018, you
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would be very cold: the North Pole base hasn't even been constructed.
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Rather, it hasn't been constructed yet. The Elves are making a little
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progress, but there's not a lot of liquid water in this climate, so they're
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getting very dehydrated. Maybe there's more underground?
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You scan a two-dimensional vertical slice of the ground nearby and discover
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that it is mostly sand with veins of clay. The scan only provides data with
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a granularity of square meters, but it should be good enough to determine
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how much water is trapped there. In the scan, x represents the distance to
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the right, and y represents the distance down. There is also a spring of
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water near the surface at x=500, y=0. The scan identifies which square
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meters are clay (your puzzle input).
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For example, suppose your scan shows the following veins of clay:
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x=495, y=2..7 y=7, x=495..501 x=501, y=3..7 x=498, y=2..4 x=506, y=1..2 x=498,
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y=10..13 x=504, y=10..13 y=13, x=498..504
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Rendering clay as #, sand as ., and the water spring as +, and with x
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increasing to the right and y increasing downward, this becomes:
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44444455555555 99999900000000 45678901234567 0 ......+....... 1
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............#. 2 .#..#.......#. 3 .#..#..#...... 4 .#..#..#...... 5
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.#.....#...... 6 .#.....#...... 7 .#######...... 8 .............. 9
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.............. 10 ....#.....#... 11 ....#.....#... 12 ....#.....#... 13
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....#######...
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The spring of water will produce water forever. Water can move through sand,
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but is blocked by clay. Water always moves down when possible, and spreads
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to the left and right otherwise, filling space that has clay on both sides
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and falling out otherwise.
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For example, if five squares of water are created, they will flow downward
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until they reach the clay and settle there. Water that has come to rest is
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shown here as ~, while sand through which water has passed (but which is now
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dry again) is shown as |:
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......+....... ......|.....#. .#..#.|.....#. .#..#.|#...... .#..#.|#......
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.#....|#...... .#~~~~~#...... .#######...... .............. ..............
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....#.....#... ....#.....#... ....#.....#... ....#######...
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Two squares of water can't occupy the same location. If another five squares
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of water are created, they will settle on the first five, filling the clay
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reservoir a little more:
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......+....... ......|.....#. .#..#.|.....#. .#..#.|#...... .#..#.|#......
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.#~~~~~#...... .#~~~~~#...... .#######...... .............. ..............
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....#.....#... ....#.....#... ....#.....#... ....#######...
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Water pressure does not apply in this scenario. If another four squares of
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water are created, they will stay on the right side of the barrier, and no
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water will reach the left side:
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......+....... ......|.....#. .#..#.|.....#. .#..#~~#...... .#..#~~#......
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.#~~~~~#...... .#~~~~~#...... .#######...... .............. ..............
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....#.....#... ....#.....#... ....#.....#... ....#######...
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At this point, the top reservoir overflows. While water can reach the tiles
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above the surface of the water, it cannot settle there, and so the next five
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squares of water settle like this:
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......+....... ......|.....#. .#..#||||...#. .#..#~~#|..... .#..#~~#|.....
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.#~~~~~#|..... .#~~~~~#|..... .#######|..... ........|..... ........|.....
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....#...|.#... ....#...|.#... ....#~~~~~#... ....#######...
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Note especially the leftmost |: the new squares of water can reach this
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tile, but cannot stop there. Instead, eventually, they all fall to the right
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and settle in the reservoir below.
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After 10 more squares of water, the bottom reservoir is also full:
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......+....... ......|.....#. .#..#||||...#. .#..#~~#|..... .#..#~~#|.....
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.#~~~~~#|..... .#~~~~~#|..... .#######|..... ........|..... ........|.....
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....#~~~~~#... ....#~~~~~#... ....#~~~~~#... ....#######...
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Finally, while there is nowhere left for the water to settle, it can reach a
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few more tiles before overflowing beyond the bottom of the scanned data:
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......+....... (line not counted: above minimum y value) ......|.....#.
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.#..#||||...#. .#..#~~#|..... .#..#~~#|..... .#~~~~~#|..... .#~~~~~#|.....
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.#######|..... ........|..... ...|||||||||.. ...|#~~~~~#|.. ...|#~~~~~#|..
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...|#~~~~~#|.. ...|#######|.. ...|.......|.. (line not counted: below
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maximum y value) ...|.......|.. (line not counted: below maximum y value)
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...|.......|.. (line not counted: below maximum y value)
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How many tiles can be reached by the water? To prevent counting forever,
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ignore tiles with a y coordinate smaller than the smallest y coordinate in
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your scan data or larger than the largest one. Any x coordinate is valid. In
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this example, the lowest y coordinate given is 1, and the highest is 13,
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causing the water spring (in row 0) and the water falling off the bottom of
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the render (in rows 14 through infinity) to be ignored.
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So, in the example above, counting both water at rest (~) and other sand
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tiles the water can hypothetically reach (|), the total number of tiles the
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water can reach is 57.
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How many tiles can the water reach within the range of y values in your
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scan?
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Your puzzle answer was 33242.
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--- Part Two ---
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After a very long time, the water spring will run dry. How much water will
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be retained?
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In the example above, water that won't eventually drain out is shown as ~, a
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total of 29 tiles.
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How many water tiles are left after the water spring stops producing water
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and all remaining water not at rest has drained?
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Your puzzle answer was 27256.
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Both parts of this puzzle are complete! They provide two gold stars: **
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At this point, you should return to your Advent calendar and try another
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puzzle.
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If you still want to see it, you can get your puzzle input.
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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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. https://adventofcode.com/2018/day/17/input
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