26 lines
930 B
Haskell
26 lines
930 B
Haskell
import qualified Data.IntMap.Strict as M
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filterSum :: Int -> M.IntMap Int -> Int
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filterSum n subMap =
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let filterMap = M.filterWithKey (\k _ -> k <= n) subMap
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in M.foldr (+) 0 filterMap
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getSubmap :: Int -> M.IntMap (M.IntMap Int) -> M.IntMap Int
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getSubmap k numMap = M.findWithDefault undefined k numMap
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insertSubmap :: Int -> M.IntMap (M.IntMap Int) -> M.IntMap (M.IntMap Int)
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insertSubmap n numMap =
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let getFilterSumInsert k subMap = M.insert k (filterSum k (getSubmap (n-k) numMap)) subMap
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subMap = foldr getFilterSumInsert M.empty [n, n-1..1]
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in M.insert n subMap numMap
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createNummap :: Int -> M.IntMap (M.IntMap Int)
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createNummap bound =
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let initialMap = M.fromList [(0, M.fromList [(0, 1)])]
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in foldr insertSubmap initialMap [bound, bound-1..1]
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main = print $
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let bound = 100
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ways = filterSum bound $ M.findWithDefault undefined bound $ createNummap bound
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in ways - 1
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