{"id":7383,"date":"2022-09-22T06:00:17","date_gmt":"2022-09-22T04:00:17","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=7383"},"modified":"2022-12-14T14:27:02","modified_gmt":"2022-12-14T12:27:02","slug":"diferencia-conjuntista-de-listas","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/diferencia-conjuntista-de-listas\/","title":{"rendered":"Diferencia conjuntista de listas"},"content":{"rendered":"

Definir la funci\u00f3n<\/p>\n

\n   diferencia :: Eq a => [a] -> [a] -> [a]\n<\/pre>\n
tal que diferencia xs ys<\/code> es la diferencia de las listas sin elementos repetidos xs<\/code> e ys<\/code>. Por ejemplo,<\/p>\n
\n   diferencia [3,2,5,6] [5,7,3,4]  ==  [2,6]\n   diferencia [3,2,5] [5,7,3,2]    ==  []\n<\/pre>\n
Soluciones<\/b><\/p>\n
A continuaci\u00f3n se muestran las soluciones en Haskell<\/a> y las soluciones en Python<\/a>.<\/p>\n
<\/a>
\nSoluciones en Haskell<\/b><\/p>\n
\nimport Data.List (nub, sort, (\\\\))\nimport qualified Data.Set as S (fromList, toList, (\\\\) )\nimport Test.QuickCheck\n\n-- 1\u00aa soluci\u00f3n\n-- ===========\n\ndiferencia1 :: Eq a => [a] -> [a] -> [a]\ndiferencia1 xs ys =\n  [x | x <- xs, x `notElem` ys]\n\n-- 2\u00aa soluci\u00f3n\n-- ===========\n\ndiferencia2 :: Ord a => [a] -> [a] -> [a]\ndiferencia2 [] _ = []\ndiferencia2 (x:xs) ys\n  | x `elem` ys = xs `diferencia2` ys\n  | otherwise   = x : xs `diferencia2` ys\n\n-- 3\u00aa soluci\u00f3n\n-- ===========\n\ndiferencia3 :: Ord a => [a] -> [a] -> [a]\ndiferencia3 = (\\\\)\n\n-- 4\u00aa soluci\u00f3n\n-- ===========\n\ndiferencia4 :: Ord a => [a] -> [a] -> [a]\ndiferencia4 xs ys =\n  S.toList (S.fromList xs S.\\\\ S.fromList ys)\n\n-- Comprobaci\u00f3n de equivalencia\n-- ============================\n\n-- La propiedad es\nprop_diferencia :: [Int] -> [Int] -> Bool\nprop_diferencia xs ys =\n  all (== sort (xs' `diferencia1` ys'))\n      [sort (xs' `diferencia2` ys'),\n       sort (xs' `diferencia3` ys'),\n       xs' `diferencia4` ys']\n  where xs' = nub xs\n        ys' = nub ys\n\n-- La comprobaci\u00f3n es\n--    \u03bb> quickCheck prop_diferencia\n--    +++ OK, passed 100 tests.\n\n-- Comparaci\u00f3n de eficiencia\n-- =========================\n\n-- La comparaci\u00f3n es\n--    \u03bb> length (diferencia1 [0..3*10^4] [1,3..3*10^4])\n--    15001\n--    (3.39 secs, 9,553,528 bytes)\n--    \u03bb> length (diferencia2 [0..3*10^4] [1,3..3*10^4])\n--    15001\n--    (2.98 secs, 9,793,528 bytes)\n--    \u03bb> length (diferencia3 [0..3*10^4] [1,3..3*10^4])\n--    15001\n--    (3.61 secs, 11,622,502,792 bytes)\n--    \u03bb> length (diferencia4 [0..3*10^4] [1,3..3*10^4])\n--    15001\n--    (0.02 secs, 10,092,832 bytes)\n<\/pre>\n
El c\u00f3digo se encuentra en GitHub<\/a>.<\/p>\n
<\/a>
\nSoluciones en Python<\/b><\/p>\n
\nfrom typing import TypeVar\nfrom timeit import Timer, default_timer\nfrom sys import setrecursionlimit\nfrom hypothesis import given, strategies as st\n\nsetrecursionlimit(10**6)\n\nA = TypeVar('A')\n\n# 1\u00aa soluci\u00f3n\n# ===========\n\ndef diferencia1(xs: list[A], ys: list[A]) -> list[A]:\n    return [x for x in xs if x not in ys]\n\n# 2\u00aa soluci\u00f3n\n# ===========\n\ndef diferencia2(xs: list[A], ys: list[A]) -> list[A]:\n    if not xs:\n        return []\n    if xs[0] in ys:\n        return diferencia2(xs[1:], ys)\n    return [xs[0]] + diferencia2(xs[1:], ys)\n\n# 3\u00aa soluci\u00f3n\n# ===========\n\ndef diferencia3(xs: list[A], ys: list[A]) -> list[A]:\n    zs = []\n    for x in xs:\n        if x not in ys:\n            zs.append(x)\n    return zs\n\n# 4\u00aa soluci\u00f3n\n# ===========\n\ndef diferencia4(xs: list[A], ys: list[A]) -> list[A]:\n    return list(set(xs) - set(ys))\n\n# Comprobaci\u00f3n de equivalencia\n# ============================\n#\n# La propiedad es\n@given(st.lists(st.integers()),\n       st.lists(st.integers()))\ndef test_diferencia(xs, ys):\n    xs1 = list(set(xs))\n    ys1 = list(set(ys))\n    assert sorted(diferencia1(xs1, ys1)) ==\\\n           sorted(diferencia2(xs1, ys1)) ==\\\n           sorted(diferencia3(xs1, ys1)) ==\\\n           sorted(diferencia4(xs1, ys1))\n\n# La comprobaci\u00f3n es\n#    src> poetry run pytest -q diferencia_conjuntista_de_listas.py\n#    1 passed in 0.39s\n\n# Comparaci\u00f3n de eficiencia\n# =========================\n\ndef tiempo(e):\n    \"\"\"Tiempo (en segundos) de evaluar la expresi\u00f3n e.\"\"\"\n    t = Timer(e, \"\", default_timer, globals()).timeit(1)\n    print(f\"{t:0.2f} segundos\")\n\n# La comparaci\u00f3n es\n#    >>> tiempo('diferencia1(list(range(0,20000)), list(range(1,20000,2)))')\n#    0.89 segundos\n#    >>> tiempo('diferencia2(list(range(0,20000)), list(range(1,20000,2)))')\n#    2.11 segundos\n#    >>> tiempo('diferencia3(list(range(0,20000)), list(range(1,20000,2)))')\n#    1.06 segundos\n#    >>> tiempo('diferencia4(list(range(0,20000)), list(range(1,20000,2)))')\n#    0.01 segundos\n<\/pre>\n
El c\u00f3digo se encuentra en GitHub<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"
Definir la funci\u00f3n diferencia :: Eq a => [a] -> [a] -> [a] tal que diferencia xs ys es la diferencia de las listas sin elementos repetidos xs e ys. Por ejemplo, diferencia [3,2,5,6] [5,7,3,4] == [2,6] diferencia [3,2,5] [5,7,3,2] == [] Soluciones A continuaci\u00f3n se muestran las soluciones en Haskell y las soluciones en…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"footnotes":"","_jetpack_memberships_contains_paid_content":false},"categories":[581],"tags":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/7383"}],"collection":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/comments?post=7383"}],"version-history":[{"count":2,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/7383\/revisions"}],"predecessor-version":[{"id":7687,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/7383\/revisions\/7687"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=7383"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=7383"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=7383"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}