28 lines
607 B
Haskell
Executable file
28 lines
607 B
Haskell
Executable file
#!/usr/bin/env runghc
|
|
|
|
import Day10
|
|
import Data.Array
|
|
import Data.IntSet (IntSet)
|
|
import qualified Data.IntSet as IntSet
|
|
|
|
main = interact (show . solve . parse)
|
|
|
|
countPaths inp = pathsFrom start
|
|
where
|
|
start = IntSet.findMax inpSet + 3
|
|
|
|
pathsFrom 0 = 1
|
|
pathsFrom x
|
|
| x < 0 = 0
|
|
| IntSet.member x allowed =
|
|
sum $ map ((!) memo) $ filter (>= 0) $ map ((-) x) [1, 2, 3]
|
|
| otherwise = 0
|
|
|
|
inpSet = IntSet.fromList inp
|
|
allowed = IntSet.insert start inpSet
|
|
|
|
memo = listArray bnds
|
|
[ pathsFrom i | i <- range bnds ]
|
|
bnds = (0, start)
|
|
|
|
solve = countPaths
|