Definir la funci\u00f3n<\/p>\n
\n interseccion :: Eq a => [a] -> [a] -> [a]\n<\/pre>\ntal que interseccion xs ys<\/code> es la intersecci\u00f3n de las listas sin elementos repetidos xs<\/code> e ys<\/code>. Por ejemplo,<\/p>\n\n interseccion [3,2,5] [5,7,3,4] == [3,5]\n interseccion [3,2,5] [9,7,6,4] == []\n<\/pre>\nSoluciones en Haskell<\/b><\/p>\n\nimport Data.List (nub, sort, intersect)\nimport qualified Data.Set as S (fromList, toList, intersection )\nimport Test.QuickCheck\n\n-- 1\u00aa soluci\u00f3n\n-- ===========\n\ninterseccion1 :: Eq a => [a] -> [a] -> [a]\ninterseccion1 xs ys =\n [x | x <- xs, x `elem` ys]\n\n-- 2\u00aa soluci\u00f3n\n-- ===========\n\ninterseccion2 :: Ord a => [a] -> [a] -> [a]\ninterseccion2 [] _ = []\ninterseccion2 (x:xs) ys\n | x `elem` ys = x : xs `interseccion2` ys\n | otherwise = xs `interseccion2` ys\n\n-- 3\u00aa soluci\u00f3n\n-- ===========\n\ninterseccion3 :: Ord a => [a] -> [a] -> [a]\ninterseccion3 = intersect\n\n-- 4\u00aa soluci\u00f3n\n-- ===========\n\ninterseccion4 :: Ord a => [a] -> [a] -> [a]\ninterseccion4 xs ys =\n S.toList (S.fromList xs `S.intersection` S.fromList ys)\n\n-- Comprobaci\u00f3n de equivalencia\n-- ============================\n\n-- La propiedad es\nprop_interseccion :: [Int] -> [Int] -> Bool\nprop_interseccion xs ys =\n all (== sort (xs' `interseccion1` ys'))\n [sort (xs' `interseccion2` ys'),\n sort (xs' `interseccion3` ys'),\n xs' `interseccion4` ys']\n where xs' = nub xs\n ys' = nub ys\n\n-- La comprobaci\u00f3n es\n-- \u03bb> quickCheck prop_interseccion\n-- +++ OK, passed 100 tests.\n\n-- Comparaci\u00f3n de eficiencia\n-- =========================\n\n-- La comparaci\u00f3n es\n-- \u03bb> length (interseccion1 [0..3*10^4] [1,3..3*10^4])\n-- 15000\n-- (2.94 secs, 6,673,360 bytes)\n-- \u03bb> length (interseccion2 [0..3*10^4] [1,3..3*10^4])\n-- 15000\n-- (3.04 secs, 9,793,440 bytes)\n-- \u03bb> length (interseccion3 [0..3*10^4] [1,3..3*10^4])\n-- 15000\n-- (5.39 secs, 6,673,472 bytes)\n-- \u03bb> length (interseccion4 [0..3*10^4] [1,3..3*10^4])\n-- 15000\n-- (0.04 secs, 8,593,176 bytes)\n<\/pre>\n