feat: part 7-1

src/AllDays.idr

@@ -12,3 +12,4 @@ import public Day5.Part1
 import public Day5.Part2
 import public Day6.Part1
 import public Day6.Part2
+import public Day7.Part1

src/Day7/Part1.idr

@@ -0,0 +1,41 @@
+module Day7.Part1
+
+import Data.List
+import Data.List1
+import Data.String
+import Data.Vect
+
+import Utils
+
+%default total
+
+--- TYPES
+
+Op : Type
+Op = Nat -> Nat -> Nat
+
+--- PARSING
+
+parseLine : String -> Maybe (Nat, List1 Nat)
+parseLine inp =
+  let (part1 ::: [part2]) = split (==':') inp
+        | _ => Nothing
+  in (,) <$> parseNat part1
+         <*> (traverse parseNat =<< fromList (words part2))
+
+parseInput : String -> Maybe (List (Nat, List1 Nat))
+parseInput = traverse parseLine . lines
+
+--- DATA
+
+search : List Op -> Nat -> List1 Nat -> Bool
+search _ n (x ::: []) = x == n
+search ops n (x ::: y :: xs) =
+  -- heuristic: abandon if running total is larger than target
+  x <= n && any (\op => assert_total $ search ops n (op x y ::: xs)) ops
+
+--- SOLUTION
+
+export
+solution : String -> Maybe Nat
+solution = map (sum . map fst . filter (uncurry $ search [(+),(*)])) . parseInput

src/Main.idr

@@ -13,7 +13,7 @@ import AllDays
 ||| The latest problem that has been solved.
 -- NOTE: UPDATE AFTER EACH SOLUTION
 latest : Problem
-latest = Pr 6 Part2
+latest = Pr 7 Part1
 
 
 solMap : SortedMap Problem (String -> String)