Day 11

.dir-locals.el

@@ -5,3 +5,5 @@
   (intero-targets "adventofcode:lib" "adventofcode:exe:adventofcode-exe" "adventofcode:test:adventofcode-test")))
 
 
+
+

adventofcode.cabal

@@ -38,6 +38,7 @@ library
       Day08
       Day09
       Day10
+      Day11
   other-modules:
       Paths_adventofcode
   build-depends:

app/Main.hs

@@ -16,6 +16,7 @@ import qualified Day07
 import qualified Day08
 import qualified Day09
 import qualified Day10
+import qualified Day11
 
 showSol :: [Char] -> Doc -> IO ()
 showSol txt d = putText . toS . render $
@@ -37,6 +38,7 @@ solutions = Map.fromList [(["01"], day01)
                          ,(["08"], day08)
                          ,(["09"], day09)
                          ,(["10"], day10)
+                         ,(["11"], day11)
                          ]
 
 day01 :: IO ()
@@ -105,3 +107,10 @@ day10 = do
   showSol "Solution 1" (int sol1)
   input2 <- Day10.parseInput2
   showSol "Solution 2" (text (toS (Day10.solution2 input2)))
+
+day11 :: IO ()
+day11 = do
+  putText "Day 11:"
+  input <- Day11.parseInput
+  let sol1 = Day11.solution1 input
+  showSol "Solution 1" (int sol1)

package.yaml

@@ -23,6 +23,7 @@ library:
   - Day08
   - Day09
   - Day10
+  - Day11
   dependencies:
   - base >=4.7 && <5
   - protolude

src/Day11.hs

@@ -0,0 +1,99 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-|
+description:
+
+--- Day 11: Hex Ed ---
+
+Crossing the bridge, you've barely reached the other side of the stream when a
+program comes up to you, clearly in distress. "It's my child process," she says,
+"he's gotten lost in an infinite grid!"
+
+Fortunately for her, you have plenty of experience with infinite grids.
+
+Unfortunately for you, it's a hex grid.
+
+The hexagons ("hexes") in this grid are aligned such that adjacent hexes can be
+found to the north, northeast, southeast, south, southwest, and northwest:
+
+  \ n  /
+nw +--+ ne
+  /    \
+-+      +-
+  \    /
+sw +--+ se
+  / s  \
+
+You have the path the child process took. Starting where he started, you need to
+determine the fewest number of steps required to reach him. (A "step" means to
+move from the hex you are in to any adjacent hex.)
+
+For example:
+
+- ne,ne,ne is 3 steps away.
+- ne,ne,sw,sw is 0 steps away (back where you started).
+- ne,ne,s,s is 2 steps away (se,se).
+- se,sw,se,sw,sw is 3 steps away (s,s,sw).
+
+--- Part Two ---
+
+How many steps away is the furthest he ever got from his starting position?
+
+|-}
+
+module Day11 where
+
+import           Protolude
+
+import qualified Data.Text as T
+import Data.List (scanl',last)
+
+data Move = NW | N | NE | SE | S | SW deriving (Show, Eq, Ord)
+
+
+parseInput :: IO [Move]
+parseInput = parseTxt <$> readFile "inputs/day11.txt"
+
+parseTxt :: Text -> [Move]
+parseTxt str = str & T.strip & T.splitOn "," & map strToMove
+  where
+    strToMove "n"  = N
+    strToMove "nw" = NW
+    strToMove "ne" = NE
+    strToMove "s"  = S
+    strToMove "sw" = SW
+    strToMove "se" = SE
+
+data Coord = Coord Int Int Int deriving (Show, Eq, Ord)
+
+direction :: Move -> Coord
+direction N  = Coord 0    1    (-1)
+direction S  = Coord 0    (-1) 1
+direction NE = Coord 1    0    (-1)
+direction SW = Coord (-1) 0    1
+direction NW = Coord (-1) 1    0
+direction SE = Coord 1    (-1) 0
+
+sumCoord :: Coord -> Coord -> Coord
+sumCoord (Coord x1 y1 z1) (Coord x2 y2 z2) =
+  Coord (x1 + x2) (y1 + y2) (z1 + z2)
+
+origin :: Coord
+origin = Coord 0 0 0
+
+dist :: Coord -> Int
+dist (Coord x1 y1 z1) =
+  (abs x1 + abs y1 + abs z1) `div` 2
+
+solution1 :: [Move] -> Int
+solution1 moves =
+  map direction moves
+  & foldl' sumCoord origin
+  & dist
+
+solution2 :: [Move] -> Int
+solution2 moves =
+  map direction moves
+  & scanl' sumCoord origin
+  & map dist
+  & maximum

test/Spec.hs

@@ -11,6 +11,7 @@ import qualified Day06
 import qualified Day07
 import qualified Day08
 import qualified Day10
+import qualified Day11
 
 
 main :: IO ()
@@ -93,4 +94,16 @@ main = defaultMain $
     , testCase "solution 2 1,2,4" $
         Day10.solution2 "1,2,4" @?= "63960835bcdc130f0b66d7ff4f6a5a8e"
     ]
+  , testGroup "Day 11"
+    [ testGroup "Solution 1"
+      [ testCase "Example 1" $
+          Day11.solution1 (Day11.parseTxt "ne,ne,ne") @?= 3
+      , testCase "Example 2" $
+         Day11.solution1 (Day11.parseTxt "ne,ne,sw,sw") @?= 0
+      , testCase "Example 3" $
+         Day11.solution1 (Day11.parseTxt "ne,ne,s,s") @?= 2
+      , testCase "Example 4" $
+         Day11.solution1 (Day11.parseTxt "se,sw,se,sw,sw") @?= 3
+      ]
+    ]
   ]