72 lines
1.8 KiB
Standard ML
72 lines
1.8 KiB
Standard ML
fun amountInStr (needle, haystack) : int =
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let
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val l = List.tabulate (size haystack, (fn i =>
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String.isPrefix needle (String.substring (haystack, i, (size haystack - i)))
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))
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in
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foldl (fn (v, acc) => if v then acc + 1 else acc) 0 l
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end
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fun reverseStr str = (String.implode o List.rev o String.explode) str
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fun wordsInLine line =
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amountInStr ("XMAS", line) + amountInStr ("XMAS", reverseStr line)
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fun wordsInLines (lines : string list) =
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foldl (op +) 0 (map wordsInLine lines)
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fun lineLength lines i = size (List.nth (lines, i))
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fun pos lines (x, y) = String.sub (List.nth (lines, y), x)
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fun column lines i =
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String.implode (List.tabulate (
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lineLength lines i,
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(fn j => pos lines (i, j))
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))
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fun nwDiagonal lines i =
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String.implode (List.tabulate (i + 1, (fn j =>
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pos lines (i - j, j)
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)))
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fun seDiagonal lines i =
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String.implode (List.tabulate (i, (fn j =>
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pos lines ((lineLength lines i) - (i - j), (lineLength lines i) - j - 1)
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)))
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fun neDiagonal lines i =
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String.implode (List.tabulate (i, (fn j =>
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pos lines ((lineLength lines i) - (i - j), j)
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)))
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fun swDiagonal lines i =
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String.implode (List.tabulate (i + 1, (fn j =>
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pos lines (i - j, (lineLength lines i) - j - 1)
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)))
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fun applyToLines f lines =
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List.tabulate (length lines, (f lines))
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val file = TextIO.openIn "day_4.txt"
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val input = TextIO.inputAll file;
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TextIO.closeIn file;
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val lines = String.tokens (fn c => c = #"\n") input
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val columns = applyToLines column lines
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val nwDiagonals = applyToLines nwDiagonal lines
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val seDiagonals = applyToLines seDiagonal lines
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val neDiagonals = applyToLines neDiagonal lines
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val swDiagonals = applyToLines swDiagonal lines
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val result =
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wordsInLines lines +
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wordsInLines columns +
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wordsInLines nwDiagonals +
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wordsInLines seDiagonals +
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wordsInLines neDiagonals +
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wordsInLines swDiagonals
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