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29 lines
660 B
29 lines
660 B
7 years ago
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#! /usr/bin/env runghc
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import qualified Data.List as L
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import qualified Data.Function as F
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import Control.Monad
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data Trie = TBranch {
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getRoot :: String,
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getChildren :: [Trie]
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}
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deriving (Show)
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notEmpty [] = False
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notEmpty _ = True
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buildTrie [] = TBranch "" []
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buildTrie words =
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let root = head $ head words
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groups = groupTails $ map tail words
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in TBranch [root] $ map buildTrie groups
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trie words = TBranch "" (map buildTrie $ groupTails $ tails words)
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groupTails [] = []
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groupTails xs = L.groupBy ((==) `F.on` head) $ L.sort $ filter notEmpty xs
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tails "" = []
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tails (w@(c:cs)) = w : tails cs
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