feat: part 8-1

src/AllDays.idr

@@ -14,3 +14,4 @@ import public Day6.Part1
 import public Day6.Part2
 import public Day7.Part1
 import public Day7.Part2
+import public Day8.Part1

src/Day8/Part1.idr

@@ -0,0 +1,54 @@
+module Day8.Part1
+
+import Data.List
+import Data.Vect
+
+import Utils
+
+%default total
+
+--- TYPES
+
+Map : (h, w : Nat) -> Type
+Map h w = Grid h w (Maybe Char)
+
+--- PARSING
+
+parseInput : String -> Maybe (h ** w ** Map h w)
+parseInput inp = do
+  (h ** w ** grid) <- parseGrid inp
+  pure (h ** w ** map (map (filter (/='.') . Just)) grid)
+
+--- DATA
+
+frequencies : Map h w -> List Char
+frequencies mp = nub $ do
+  row <- toList mp
+  Just c <- toList row
+    | Nothing => empty
+  pure c
+
+antinodePos : {h, w : _} -> (a, b : Pos h w) -> Maybe (Pos h w)
+antinodePos (x, y) (x', y') =
+  (,) <$> integerToFin (cast x * 2 - cast x') h
+      <*> integerToFin (cast y * 2 - cast y') w
+
+antinodes : {h, w : _} -> Map h w -> Char -> List (Pos h w)
+antinodes mp c = do
+  let poss = do
+        i <- allFins h
+        j <- allFins w
+        guard (index (i, j) mp == Just c)
+        pure (i, j)
+  p1 <- poss
+  p2 <- poss
+  guard (p1 /= p2)
+  toList (antinodePos p1 p2) <|> toList (antinodePos p2 p1)
+
+--- SOLUTION
+
+export
+solution : String -> Maybe Nat
+solution inp = do
+  (h ** w ** mp) <- parseInput inp
+  pure $ length $ nub $ frequencies mp >>= antinodes mp

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 7 Part2
+latest = Pr 8 Part1
 
 
 solMap : SortedMap Problem (String -> String)