blob: 1191d1734acddcbd0a33f725af213cfc4af5962b (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
|
import qualified Data.Map.Strict as Map
main :: IO ()
main = do
s0 <- map (read @Int) . words <$> getContents
let ndigs10 0 = 1
ndigs10 n = pre (4::Int)
where pre p | n >= 10 ^ p = pre (2*p)
| otherwise = bin 0 p
bin lo hi | lo == hi - 1 = hi
| n >= 10 ^ mid = bin mid hi
| otherwise = bin lo mid
where mid = (lo + hi) `quot` 2
let splitHalf n =
let nd = ndigs10 n
in if even nd then Just $ n `quotRem` (10 ^ (ndigs10 n `quot` 2))
else Nothing
let blink =
Map.fromListWith (+)
. concatMap (\(n, c) ->
if n == 0 then [(1, c)]
else case splitHalf n of
Just (n1, n2) -> [(n1, c), (n2, c)]
Nothing -> [(n * 2024, c)])
. Map.assocs
print $ sum . Map.elems $ iterate blink (Map.fromList (map (,1::Int) s0)) !! 25
print $ sum . Map.elems $ iterate blink (Map.fromList (map (,1) s0)) !! 75
|
