Reimar/adventofcode-2024
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WIP refactor day 3

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Reimar 2024-12-06 16:41:54 +01:00
parent 5b21b1db58
commit 70c49f3d3c
Signed by: Reimar
GPG Key ID: 93549FA07F0AE268
1 changed files with 23 additions and 17 deletions
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40
day_3.sml
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@ -1,30 +1,36 @@
datatype instruction = NOOP | DO | DONT | MUL of (int * int)
fun numberAt (i : int) = fn (s : string) =>
if i >= String.size s then NONE
else SOME (Substring.takel Char.isDigit (Substring.extract (s, i, NONE)))
fun substrToInt (n : substring) = valOf (Int.fromString (Substring.string n))
fun startsWith (needle : string, haystack : string, pos : int) =
size haystack > pos + size needle andalso String.substring (haystack, pos, size needle) = needle
fun sum (l : int list) : int = foldl (op +) 0 l
fun substrToInt (n : substring) = valOf (Int.fromString (Substring.string n))
val file = TextIO.openIn "day_3.txt"
val input = TextIO.inputAll file;
TextIO.closeIn file;
val instructions = List.tabulate ((size input), (fn i =>
let
val n1 = numberAt (i + 4) input
val n2 = Option.mapPartial (fn n => numberAt (i + 5 + Substring.size n) input) n1
in
if isSome n1 andalso isSome n2 andalso
String.substring (input, i, 4) = "mul(" andalso
String.sub (input, i + 4 + Substring.size (valOf n1)) = #"," andalso
String.sub (input, i + 5 + Substring.size (valOf n1) + Substring.size (valOf n2)) = #")"
then SOME (n1, n2) else NONE
end))
if startsWith ("do()", input, i) then DO
else if startsWith ("don't()", input, i) then DONT
else
let
val n1 = numberAt (i + 4) input
val n2 = Option.mapPartial (fn n => numberAt (i + 5 + Substring.size n) input) n1
in
case (n1, n2) of
(SOME(a), SOME(b)) =>
if
startsWith ("mul(", input, i) andalso
String.sub (input, i + 4 + Substring.size a) = #"," andalso
String.sub (input, i + 5 + Substring.size a + Substring.size b) = #")"
then MUL (substrToInt a, substrToInt b) else NOOP
| _ => NOOP
end
))
val instructions = List.mapPartial
(fn (num) => case num of SOME (SOME x, SOME y) => SOME (substrToInt x, substrToInt y) | _ => NONE)
instructions
val result = sum (map (op *) instructions)
val result = foldl (fn (ins, v) => case ins of MUL (a, b) => v + a + b | _ => v) 0 instructions