59 lines
1.7 KiB
Text
59 lines
1.7 KiB
Text
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Day 24 Notes
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+--------+
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| Part 1 |
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+--------+
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$ elixir day24part1.exs
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326
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Thoughts:
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Interesting. Need to work out how to implement a hexagonal grid.
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Use Enum.chunk_while to parse the variable-length `e`, `ne`, `s', `sw` etc. input tokens.
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I decided to do it like this: Use x, y coordinates, but horizontally adjacent cells are 2 x units
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apart. Diagonally adjacent cells are 1 x unit and 1 y unit apart.
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/ \ (0,0)
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/ \ / \ (1, -1)
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\ / \ /
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↑
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(-1, -1)
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Define a tranlation vector for each direction, then we can walk the directions, and take the sum
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of all the translations.
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Store the black cells in a MapSet, and count them once we're done.
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+--------+
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| Part 2 |
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+--------+
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$ elixir day24part2.exs
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3979
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Thoughts:
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More complicated now, because we actually have to iterate all the black/white cells and their
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neighbours. Calculating the grid extremities looks complicated due to the hexagonal properties.
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However, this is very similar to Day 17 Part 2, so I will just adapt that solution for here too:
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1. For all current black squares, check the neighbours to see what its next state should be.
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- additionally keep track of which white squares we identified.
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2. As white cells must have a black neighbour to be flipped, we know that it's fine to only
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check white cells that are next to a black cell. So iterate the white cells we encountered
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in step 1, and check their neighbours too.
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+------------------+
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| Overall Thoughts |
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+------------------+
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Let another game of life. 3rd time this year? This one was a bit more interesting due to the
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hexagonal nature, but part two was almost the same as Day 17. Maybe that's a good reflection
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on my day 17 implementation, though.
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