initial day 9

Author: mstksg

README.md

@@ -42,7 +42,7 @@ haddocks][haddock] --- more info below!
 | Day 2 | [x][d02r] | [x][d02g] | [x][d02h] | [x][d02b] |
 | Day 3 | | [x][d03g] | [x][d03h] | [x][d03b] |
 | Day 4 | | [x][d04g] | [x][d04h] | [x][d04b] |
-| Day 5 | |  | |  |
+| Day 5 | | [x][d05g] | [x][d05h] | [x][d05b] |
 | Day 6 | | [x][d06g] | [x][d06h] | [x][d06b] |
 | Day 7 | | [x][d07g] | [x][d07h] | [x][d07b] |
 | Day 8 | | [x][d08g] | [x][d08h] | [x][d08b] |
@@ -309,6 +309,9 @@ All networking features are powered by *[advent-of-code-api][]*.
 [d04g]: https://github.com/mstksg/advent-of-code-2021/blob/master/src/AOC/Challenge/Day04.hs
 [d04h]: https://mstksg.github.io/advent-of-code-2021/src/AOC.Challenge.Day04.html
 [d04b]: https://github.com/mstksg/advent-of-code-2021/blob/master/reflections.md#day-4-benchmarks
+[d05g]: https://github.com/mstksg/advent-of-code-2021/blob/master/src/AOC/Challenge/Day05.hs
+[d05h]: https://mstksg.github.io/advent-of-code-2021/src/AOC.Challenge.Day05.html
+[d05b]: https://github.com/mstksg/advent-of-code-2021/blob/master/reflections.md#day-5-benchmarks
 [d06g]: https://github.com/mstksg/advent-of-code-2021/blob/master/src/AOC/Challenge/Day06.hs
 [d06h]: https://mstksg.github.io/advent-of-code-2021/src/AOC.Challenge.Day06.html
 [d06b]: https://github.com/mstksg/advent-of-code-2021/blob/master/reflections.md#day-6-benchmarks

reflections.md

@@ -25,6 +25,7 @@ Table of Contents
 * [Day 2](#day-2)
 * [Day 3](#day-3) *(no reflection yet)*
 * [Day 4](#day-4) *(no reflection yet)*
+* [Day 5](#day-5) *(no reflection yet)*
 * [Day 6](#day-6) *(no reflection yet)*
 * [Day 7](#day-7) *(no reflection yet)*
 * [Day 8](#day-8) *(no reflection yet)*
@@ -389,6 +390,50 @@ variance introduced by outliers: 59% (severely inflated)
 
 
 
+Day 5
+------
+
+<!--
+This section is generated and compiled by the build script at ./Build.hs from
+the file `./reflections/day05.md`. If you want to edit this, edit
+that file instead!
+-->
+
+*[Prompt][d05p]* / *[Code][d05g]* / *[Rendered][d05h]* / *[Standalone Reflection Page][d05r]*
+
+[d05p]: https://adventofcode.com/2021/day/5
+[d05g]: https://github.com/mstksg/advent-of-code-2021/blob/master/src/AOC/Challenge/Day05.hs
+[d05h]: https://mstksg.github.io/advent-of-code-2021/src/AOC.Challenge.Day05.html
+[d05r]: https://github.com/mstksg/advent-of-code-2021/blob/master/reflections-out/day05.md
+
+*Reflection not yet written -- please check back later!*
+
+### Day 5 Benchmarks
+
+```
+>> Day 05a
+benchmarking...
+time 5.318 ms (5.256 ms .. 5.390 ms)
+ 0.998 R² (0.997 R² .. 0.999 R²)
+mean 5.236 ms (5.194 ms .. 5.298 ms)
+std dev 149.2 μs (117.1 μs .. 207.5 μs)
+variance introduced by outliers: 12% (moderately inflated)
+
+* parsing and formatting times excluded
+
+>> Day 05b
+benchmarking...
+time 11.37 ms (11.19 ms .. 11.58 ms)
+ 0.997 R² (0.995 R² .. 0.999 R²)
+mean 11.48 ms (11.36 ms .. 11.73 ms)
+std dev 417.9 μs (285.5 μs .. 608.1 μs)
+variance introduced by outliers: 13% (moderately inflated)
+
+* parsing and formatting times excluded
+```
+
+
+
 Day 6
 ------
 

src/AOC/Challenge/Day05.hs

@@ -100,6 +100,14 @@ day05b = day05 id
 -- solve y = (4-0)`div`2 = 2
 -- and so check if 2 is in range
 
+-- sloped: <t, z+m*t>
+-- intersect with other slope:
+-- <t, z1 + m1 * t> == <t, z2 + m2 * t> (t = x = equal)
+-- solve: z1 + m1 * t == z2 + m2 * t
+-- m1 * t = m2 * t + (z2 - z1)
+-- t = (m2 * t + z2 - z1) / m1
+--
+
 overlaps :: Line -> Line -> [V2 Integer]
 overlaps = \case
  Line Horiz y1 rx1 -> \case

src/AOC/Challenge/Day09.hs

@@ -22,8 +22,8 @@
 -- will recommend what should go in place of the underscores.
 
 module AOC.Challenge.Day09 (
- -- day09a
- -- , day09b
+ day09a
+ , day09b
  ) where
 
 import AOC.Prelude
@@ -47,14 +47,52 @@ import qualified Text.Megaparsec.Char.Lexer as PP
 
 day09a :: _ :~> _
 day09a = MkSol
- { sParse = Just . lines
+ { sParse = Just . parseAsciiMap (Just . digitToInt)
  , sShow = show
- , sSolve = Just
- }
+ , sSolve = \xs -> Just . sum $ M.mapWithKey (go xs) xs
+ } 
+ where
+ go mp p i 
+ | and $ mapMaybe f (cardinalNeighbs p) = (i+1)
+ | otherwise = 0
+ where
+ f q = case M.lookup q mp of
+ Nothing -> Nothing
+ Just j -> Just $ j > i
+-- cardinalNeighbs :: Point -> [Point]
+
+
+ -- go xs = sum $ zipWith3 f xs (drop 1 xs) (drop 2 xs)
+ -- where
+ -- f a b c
+ -- | a > b && c > b = 1 + b
+ -- | otherwise = 0
 
 day09b :: _ :~> _
 day09b = MkSol
- { sParse = sParse day09a
+ { sParse = Just . parseAsciiMap (Just . digitToInt)
  , sShow = show
- , sSolve = Just
- }
+ , sSolve = \xs -> Just $
+ let lowpoints = M.keys $ M.filterWithKey (go xs) xs
+ in product . take 3 . reverse . sort . map (S.size . floodFill (spreadout xs) . S.singleton) $ lowpoints
+ } 
+ where
+ go mp p i = and $ mapMaybe f (cardinalNeighbs p)
+ where
+ f q = case M.lookup q mp of
+ Nothing -> Nothing
+ Just j -> Just $ j > i
+ spreadout mp p = S.fromList . filter valid . cardinalNeighbs $ p
+ where
+ valid q = case M.lookup q mp of
+ Nothing -> False
+ Just i -> i /= 9
+
+
+-- -- | Flood fill from a starting set
+-- floodFill
+-- :: Ord a
+-- => (a -> Set a) -- ^ Expansion (be sure to limit allowed points)
+-- -> Set a -- ^ Start points
+-- -> Set a -- ^ Flood filled
+-- floodFill f = snd . floodFillCount f

test-data/2021/09a.txt

@@ -0,0 +1,6 @@
+2199943210
+3987894921
+9856789892
+8767896789
+9899965678
+>>> 15

test-data/2021/09b.txt

@@ -0,0 +1,6 @@
+2199943210
+3987894921
+9856789892
+8767896789
+9899965678
+>>> 1134