105 lines
2.7 KiB
Markdown
105 lines
2.7 KiB
Markdown
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## \-\-- Day 4: Ceres Search \-\--
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\"Looks like the Chief\'s not here. Next!\" One of The Historians pulls
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out a device and pushes the only button on it. After a brief flash, you
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recognize the interior of the [Ceres monitoring station](/2019/day/10)!
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As the search for the Chief continues, a small Elf who lives on the
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station tugs on your shirt; she\'d like to know if you could help her
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with her *word search* (your puzzle input). She only has to find one
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word: `XMAS`.
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This word search allows words to be horizontal, vertical, diagonal,
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written backwards, or even overlapping other words. It\'s a little
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unusual, though, as you don\'t merely need to find one instance of
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`XMAS` - you need to find *all of them*. Here are a few ways `XMAS`
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might appear, where irrelevant characters have been replaced with `.`:
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..X...
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.SAMX.
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.A..A.
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XMAS.S
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.X....
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The actual word search will be full of letters instead. For example:
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MMMSXXMASM
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MSAMXMSMSA
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AMXSXMAAMM
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MSAMASMSMX
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XMASAMXAMM
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XXAMMXXAMA
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SMSMSASXSS
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SAXAMASAAA
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MAMMMXMMMM
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MXMXAXMASX
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In this word search, `XMAS` occurs a total of `18` times; here\'s the
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same word search again, but where letters not involved in any `XMAS`
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have been replaced with `.`:
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....XXMAS.
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.SAMXMS...
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...S..A...
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..A.A.MS.X
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XMASAMX.MM
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X.....XA.A
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S.S.S.S.SS
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.A.A.A.A.A
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..M.M.M.MM
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.X.X.XMASX
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Take a look at the little Elf\'s word search. *How many times does
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`XMAS` appear?*
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Your puzzle answer was `2378`.
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## \-\-- Part Two \-\-- {#part2}
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The Elf looks quizzically at you. Did you misunderstand the assignment?
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Looking for the instructions, you flip over the word search to find that
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this isn\'t actually an `XMAS` puzzle; it\'s an
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`X-MAS`
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puzzle in which you\'re supposed to find two `MAS` in the shape of an
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`X`. One way to achieve that is like this:
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M.S
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.A.
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M.S
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Irrelevant characters have again been replaced with `.` in the above
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diagram. Within the `X`, each `MAS` can be written forwards or
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backwards.
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Here\'s the same example from before, but this time all of the `X-MAS`es
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have been kept instead:
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.M.S......
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..A..MSMS.
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.M.S.MAA..
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..A.ASMSM.
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.M.S.M....
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..........
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S.S.S.S.S.
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.A.A.A.A..
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M.M.M.M.M.
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..........
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In this example, an `X-MAS` appears `9` times.
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Flip the word search from the instructions back over to the word search
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side and try again. *How many times does an `X-MAS` appear?*
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Your puzzle answer was `1796`.
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Both parts of this puzzle are complete! They provide two gold stars:
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\*\*
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At this point, you should [return to your Advent calendar](/2024) and
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try another puzzle.
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If you still want to see it, you can [get your puzzle
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input](4/input).
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