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48 lines
1.2 KiB
48 lines
1.2 KiB
#! /usr/bin/env runghc
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import qualified Data.List as L
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{-
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- Construct a suffix tree of a given word
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- See: http://www.geeksforgeeks.org/pattern-searching-set-8-suffix-tree-introduction/
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-}
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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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compress t@(TBranch root []) = t
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compress (TBranch root (child:[])) =
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let compressed = compress child
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in TBranch
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(root++(getRoot compressed))
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(getChildren compressed)
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compress (TBranch root children) = TBranch root (map compress children)
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notEmpty [] = False
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notEmpty _ = True
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buildTrie [] = TBranch "" []
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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 grouper $ L.sort xs
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where grouper [] [] = True
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grouper [] _ = False
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grouper _ [] = False
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grouper a b = (head a) == (head b)
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tails "" = []
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tails (w@(c:cs)) = w : tails cs
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suffixTree word = compress $ trie word
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