Solve day 3 part 1

day_1.sml

@@ -1,6 +1,6 @@
-fun sortAsc (l: int list) : int list = ListMergeSort.sort (op >) l
+fun sortAsc (l : int list) : int list = ListMergeSort.sort (op >) l
 
-fun sum (l: int list) : int = foldl (op +) 0 l
+fun sum (l : int list) : int = foldl (op +) 0 l
 
 fun substrToInt (substr: substring) : int = valOf (Int.fromString (Substring.string substr))
 
@@ -11,18 +11,18 @@ TextIO.closeIn file;
 val lines = String.tokens (fn (char) => char = #"\n") input
 
 val pairs = map
-    (fn (line) =>
-        let val substr = Substring.extract (line, 0, NONE)
-        in [
-            substrToInt (Substring.takel Char.isDigit substr),
-            substrToInt (Substring.taker Char.isDigit substr)
-        ] end
-    )
-    lines
+  (fn (line) =>
+    let val substr = Substring.extract (line, 0, NONE)
+    in [
+      substrToInt (Substring.takel Char.isDigit substr),
+      substrToInt (Substring.taker Char.isDigit substr)
+    ] end
+  )
+  lines
 
 val lists = (
-    sortAsc (map (fn (pair) => hd pair) pairs),
-    sortAsc (map (fn (pair) => List.last pair) pairs)
+  sortAsc (map (fn (pair) => hd pair) pairs),
+  sortAsc (map (fn (pair) => List.last pair) pairs)
 )
 
 (* Part 1 *)
@@ -34,11 +34,11 @@ val totalDistance = sum distances
 (* Part 2 *)
 
 val similarities = ListPair.map
-    (fn (n1, n2) =>
-        let val frequency = List.length (List.filter (fn (n) => n = n1) (#2 lists))
-        in n1 * frequency end
-    )
-    lists
+  (fn (n1, n2) =>
+    let val frequency = List.length (List.filter (fn (n) => n = n1) (#2 lists))
+    in n1 * frequency end
+  )
+  lists
 
 val similarityScore = sum similarities
 

day_2.sml

@@ -1,14 +1,14 @@
 fun deleteNth (l : int list, n : int) = List.take (l, n) @ List.drop (l, n + 1)
 
 fun isDecreasing (l : int list) =
-    ListPair.all (fn (a, b) => b < a andalso b >= a - 3) (l, tl l)
+  ListPair.all (fn (a, b) => b < a andalso b >= a - 3) (l, tl l)
 
 fun isIncreasing (l : int list) =
-    ListPair.all (fn (a, b) => b > a andalso b <= a + 3) (l, tl l)
+  ListPair.all (fn (a, b) => b > a andalso b <= a + 3) (l, tl l)
 
 fun withTolerance (f : (int list) -> bool) = fn (l : int list) =>
-    let val withRemoved = List.tabulate (List.length l, fn (i) => deleteNth (l, i))
-    in List.exists f withRemoved end
+  let val withRemoved = List.tabulate (List.length l, fn (i) => deleteNth (l, i))
+  in List.exists f withRemoved end
 
 val file = TextIO.openIn "day_2.txt"
 val input = TextIO.inputAll file;
@@ -17,11 +17,11 @@ TextIO.closeIn file;
 val lines = String.tokens (fn (char) => char = #"\n") input
 
 val reports = map
-    (fn (line) =>
-        let val numbers = String.tokens Char.isSpace line
-        in map (fn (n) => valOf (Int.fromString n)) numbers end
-    )
-    lines
+  (fn (line) =>
+    let val numbers = String.tokens Char.isSpace line
+    in map (fn (n) => valOf (Int.fromString n)) numbers end
+  )
+  lines
 
 (* Part 1 *)
 
@@ -32,8 +32,8 @@ val safeAmount = List.length safeReports
 (* Part 2 *)
 
 val toleratedReports = List.filter
-    (fn (report) => withTolerance isDecreasing report orelse withTolerance isIncreasing report)
-    reports
+  (fn (report) => withTolerance isDecreasing report orelse withTolerance isIncreasing report)
+  reports
 
 val toleratedAmount = List.length toleratedReports
 

day_3.sml

@@ -0,0 +1,30 @@
+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 sum (l : int list) : int = foldl (op +) 0 l
+
+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))
+
+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)
+