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    1 {-|
    2 Module:      Y2015.D17
    3 Description: Advent of Code Day 17 Solutions.
    4 License:     MIT
    5 Maintainer:  @tylerjl
    6 
    7 Solutions to the day 17 set of problems for <adventofcode.com>.
    8 -}
    9 
   10 module Y2015.D17 (filledAmong, minFilledAmong) where
   11 
   12 import Data.Function (on)
   13 import Data.List (subsequences, minimumBy)
   14 
   15 -- |Finds how many combinations of containers can fit a volume of nog
   16 filledAmong :: Int    -- ^ Length
   17             -> String -- ^ List of container sizes
   18             -> Int    -- ^ Number of combinations
   19 filledAmong t = containersBy length t . c
   20     where c = map read . lines
   21 
   22 -- |Finds how many combinations of containers the ideal combination can
   23 -- |fit a volume of nog
   24 minFilledAmong :: Int    -- ^ Length
   25                -> String -- ^ List of container sizes
   26                -> Int    -- ^ Number of combinations
   27 minFilledAmong t s =  containersBy (length . filter ((==) minFilled . length)) t c
   28     where c         = map read $ lines s
   29           minFilled = containersBy (length . minimumBy (compare `on` length))  t c
   30 
   31 containersBy :: ([[Int]] -> a) -> Int -> [Int] -> a
   32 containersBy f t s = f [x | x <- subsequences s, sum x == t]