{"id":7733,"date":"2022-12-20T06:00:09","date_gmt":"2022-12-20T04:00:09","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=7733"},"modified":"2022-12-19T18:31:48","modified_gmt":"2022-12-19T16:31:48","slug":"20-dic-22","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/20-dic-22\/","title":{"rendered":"Imagen especular de un \u00e1rbol binario"},"content":{"rendered":"<p>El \u00e1rbol binario<\/p>\n<pre lang=\"text\">\n        9\n       \/ \\\n      \/   \\\n     3     7\n    \/ \\\n   2   4\n<\/pre>\n<p>se puede representar por<\/p>\n<pre lang=\"text\">\n   N 9 (N 3 (H 2) (H 4)) (H 7)\n<\/pre>\n<p>El tipo de los \u00e1rboles binarios se puede definir por<\/p>\n<pre lang=\"text\">\n   data Arbol a = H a\n                | N a (Arbol a) (Arbol a)\n     deriving (Show, Eq)\n<\/pre>\n<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   espejo :: Arbol a -> Arbol a\n<\/pre>\n<p>tal que <code>espejo x<\/code> es la imagen especular del \u00e1rbol <code>x<\/code>. Por ejemplo,<\/p>\n<pre lang=\"text\">\n   espejo (N 9 (N 3 (H 2) (H 4)) (H 7)) == N 9 (H 7) (N 3 (H 4) (H 2))\n<\/pre>\n<p>Comprobar con QuickCheck las siguientes propiedades, para todo \u00e1rbol <code>x<\/code>,<\/p>\n<pre lang=\"text\">\n   espejo (espejo x) = x\n   reverse (preorden (espejo x)) = postorden x\n   postorden (espejo x) = reverse (preorden x)\n<\/pre>\n<p><b>Soluciones<\/b><\/p>\n<p>A continuaci\u00f3n se muestran las <a href=\"#haskell\">soluciones en Haskell<\/a> y las <a href=\"#python\">soluciones en Python<\/a>.<\/p>\n<p><a name=\"haskell\"><\/a><br \/>\n<b>Soluciones en Haskell<\/b><\/p>\n<pre lang=\"haskell\">\nimport Test.QuickCheck\n\ndata Arbol a = H a\n             | N a (Arbol a) (Arbol a)\n  deriving (Show, Eq)\n\nespejo :: Arbol a -> Arbol a\nespejo (H x)     = H x\nespejo (N x i d) = N x (espejo d) (espejo i)\n\n-- Generador para las comprobaciones\n-- =================================\n\n-- (arbolArbitrario n) es un \u00e1rbol aleatorio de altura n. Por ejemplo,\n--    \u03bb> sample (arbolArbitrario 3 :: Gen (Arbol Int))\n--    N 0 (H 0) (H 0)\n--    N 1 (N (-2) (H (-1)) (H 1)) (H 2)\n--    N 3 (H 1) (H 2)\n--    N 6 (N 0 (H 5) (H (-5))) (N (-5) (H (-5)) (H 4))\n--    H 7\n--    N (-8) (H (-8)) (H 9)\n--    H 2\n--    N (-1) (H 7) (N 9 (H (-2)) (H (-8)))\n--    H (-3)\n--    N 0 (N 16 (H (-14)) (H (-18))) (H 7)\n--    N (-16) (H 18) (N (-19) (H (-15)) (H (-18)))\narbolArbitrario :: Arbitrary a => Int -> Gen (Arbol a)\narbolArbitrario 0 = H <$> arbitrary\narbolArbitrario n =\n  oneof [H <$> arbitrary,\n         N <$> arbitrary <*> arbolArbitrario (div n 2) <*> arbolArbitrario (div n 2)]\n\n-- Arbol es subclase de Arbitrary\ninstance Arbitrary a => Arbitrary (Arbol a) where\n  arbitrary = sized arbolArbitrario\n\n-- Funciones auxiliares para la comprobaci\u00f3n\n-- =========================================\n\n-- (preorden x) es la lista correspondiente al recorrido preorden del\n-- \u00e1rbol x; es decir, primero visita la ra\u00edz del \u00e1rbol, a continuaci\u00f3n\n-- recorre el sub\u00e1rbol izquierdo y, finalmente, recorre el sub\u00e1rbol\n-- derecho. Por ejemplo,\n--    preorden (N 9 (N 3 (H 2) (H 4)) (H 7))  ==  [9,3,2,4,7]\npreorden :: Arbol a -> [a]\npreorden (H x)     = [x]\npreorden (N x i d) = x : preorden i ++ preorden d\n\n-- (postorden x) es la lista correspondiente al recorrido postorden\n-- del \u00e1rbol x; es decir, primero recorre el sub\u00e1rbol izquierdo, a\n-- continuaci\u00f3n el sub\u00e1rbol derecho y, finalmente, la ra\u00edz del\n-- \u00e1rbol. Por ejemplo,\n--    postorden (N 9 (N 3 (H 2) (H 4)) (H 7))  ==  [2,4,3,7,9]\npostorden :: Arbol a -> [a]\npostorden (H x)     = [x]\npostorden (N x i d) = postorden i ++ postorden d ++ [x]\n\n-- Comprobaci\u00f3n de las propiedades\n-- ===============================\n\n-- Las propiedades son\nprop_espejo :: Arbol Int -> Bool\nprop_espejo x =\n  espejo (espejo x) == x &&\n  reverse (preorden (espejo x)) == postorden x &&\n  postorden (espejo x) == reverse (preorden x)\n\n-- La comprobaci\u00f3n es\n--    \u03bb> quickCheck prop_espejo\n--    OK, passed 100 tests.\n<\/pre>\n<p><a name=\"python\"><\/a><br \/>\n<b>Soluciones en Python<\/b><\/p>\n<pre lang=\"python\">\nfrom dataclasses import dataclass\nfrom random import choice, randint\nfrom typing import Generic, TypeVar\n\nfrom hypothesis import given\nfrom hypothesis import strategies as st\n\nA = TypeVar(\"A\")\n\n@dataclass\nclass Arbol(Generic[A]):\n    pass\n\n@dataclass\nclass H(Arbol[A]):\n    x: A\n\n@dataclass\nclass N(Arbol[A]):\n    x: A\n    i: Arbol[A]\n    d: Arbol[A]\n\ndef espejo(a: Arbol[A]) -> Arbol[A]:\n    match a:\n        case H(x):\n            return H(x)\n        case N(x, i, d):\n            return N(x, espejo(d), espejo(i))\n    assert False\n\n# Generador para las comprobaciones\n# =================================\n\n# (arbolArbitrario n) es un \u00e1rbol aleatorio de orden n. Por ejemplo,\n#    >>> arbolArbitrario(4)\n#    N(x=2, i=H(x=1), d=H(x=9))\n#    >>> arbolArbitrario(4)\n#    H(x=10)\n#    >>> arbolArbitrario(4)\n#    N(x=4, i=N(x=7, i=H(x=4), d=H(x=0)), d=H(x=6))\ndef arbolArbitrario(n: int) -> Arbol[int]:\n    if n <= 1:\n        return H(randint(0, 10))\n    m = n \/\/ 2\n    return choice([H(randint(0, 10)),\n                   N(randint(0, 10),\n                     arbolArbitrario(m),\n                     arbolArbitrario(m))])\n\n# Funciones auxiliares para la comprobaci\u00f3n\n# =========================================\n\n# preorden(x) es la lista correspondiente al recorrido preorden del\n# \u00e1rbol x; es decir, primero visita la ra\u00edz del \u00e1rbol, a continuaci\u00f3n\n# recorre el sub\u00e1rbol izquierdo y, finalmente, recorre el sub\u00e1rbol\n# derecho. Por ejemplo,\n#    >>> preorden(N(9, N(3, H(2), H(4)), H(7)))\n#    [9, 3, 2, 4, 7]\ndef preorden(a: Arbol[A]) -> list[A]:\n    match a:\n        case H(x):\n            return [x]\n        case N(x, i, d):\n            return [x] + preorden(i) + preorden(d)\n    assert False\n\n# (postorden x) es la lista correspondiente al recorrido postorden\n# del \u00e1rbol x; es decir, primero recorre el sub\u00e1rbol izquierdo, a\n# continuaci\u00f3n el sub\u00e1rbol derecho y, finalmente, la ra\u00edz del\n# \u00e1rbol. Por ejemplo,\n#    >>> postorden(N(9, N(3, H(2), H(4)), H(7)))\n#    [2, 4, 3, 7, 9]\ndef postorden(a: Arbol[A]) -> list[A]:\n    match a:\n        case H(x):\n            return [x]\n        case N(x, i, d):\n            return postorden(i) + postorden(d) + [x]\n    assert False\n\n# Comprobaci\u00f3n de las propiedades\n# ===============================\n\n# Las propiedades son\n@given(st.integers(min_value=1, max_value=10))\ndef test_espejo(n: int) -> None:\n    x = arbolArbitrario(n)\n    assert espejo(espejo(x)) == x\n    assert list(reversed(preorden(espejo(x)))) == postorden(x)\n    assert postorden(espejo(x)) == list(reversed(preorden(x)))\n\n# La comprobaci\u00f3n es\n#    src> poetry run pytest -q imagen_especular_de_un_arbol_binario.py\n#    1 passed in 0.16s\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>El \u00e1rbol binario 9 \/ \\ \/ \\ 3 7 \/ \\ 2 4 se puede representar por N 9 (N 3 (H 2) (H 4)) (H 7) El tipo de los \u00e1rboles binarios se puede definir por data Arbol a = H a | N a (Arbol a) (Arbol a) deriving (Show, Eq) Definir&#8230;<\/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\/7733"}],"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=7733"}],"version-history":[{"count":1,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/7733\/revisions"}],"predecessor-version":[{"id":7734,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/7733\/revisions\/7734"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=7733"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=7733"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=7733"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}