Created
August 18, 2024 17:07
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| module NextBiggerSpec (spec) where | |
| import Test.Hspec | |
| import Test.QuickCheck | |
| import NextBigger (nextBigger) | |
| import Data.List (sort,unfoldr) | |
| import Data.Tuple (swap) | |
| import Data.Maybe (isJust,fromJust) | |
| spec :: Spec | |
| spec = do | |
| it "example tests" $ do | |
| nextBigger 12 `shouldBe` 21 | |
| nextBigger 513 `shouldBe` 531 | |
| nextBigger 2017 `shouldBe` 2071 | |
| nextBigger 414 `shouldBe` 441 | |
| nextBigger 144 `shouldBe` 414 | |
| it "fixed tests" $ do | |
| nextBigger 123456789 `shouldBe` 123456798 | |
| nextBigger 1234567890 `shouldBe` 1234567908 | |
| nextBigger 9876543210 `shouldBe` -1 | |
| nextBigger 9999999999 `shouldBe` -1 | |
| nextBigger 59884848459853 `shouldBe` 59884848483559 | |
| it "random tests" $ do | |
| property $ withMaxSuccess 140 $ forAll (oneof [genArg,sortDesc <$> genArg]) $ \ n -> do | |
| -- print (n,refNextBigger n) | |
| nextBigger n `shouldBe` refNextBigger n | |
| genArg :: Gen Int | |
| genArg = do e <- choose (1,14 :: Int) ; choose (1,10^e-1) | |
| sortDesc :: Int -> Int | |
| sortDesc n = foldr ( \ v z -> 10 * z + v ) 0 $ sort $ unfoldr mod10 n where | |
| mod10 0 = Nothing | |
| mod10 n = Just $ swap $ n `divMod` 10 | |
| refNextBigger :: Int -> Int | |
| refNextBigger n = maybe (-1) ( const $ read $ hd ++ mv : replace mv pvt (reverse tl) ) i where | |
| s = show n | |
| i = foldr ( \ (i,c,d) z -> if isJust z then z else if c < d then Just i else Nothing ) Nothing $ zip3 [0..] s (tail s) | |
| (hd,pvt:tl) = splitAt (fromJust i) s | |
| mv = minimum $ filter (> pvt) tl | |
| replace _ _ [] = error "replace: needle not found in haystack" | |
| replace needle replacement (hay:stack) | hay == needle = replacement : stack | |
| | otherwise = hay : replace needle replacement stack |
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