{"id":5256,"date":"2019-12-17T05:30:50","date_gmt":"2019-12-17T03:30:50","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=5256"},"modified":"2019-12-24T07:50:24","modified_gmt":"2019-12-24T05:50:24","slug":"interseccion-de-listas-infinitas-crecientes","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/interseccion-de-listas-infinitas-crecientes\/","title":{"rendered":"Intersecci\u00f3n de listas infinitas crecientes"},"content":{"rendered":"<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   interseccion :: Ord a => [[a]] -> [a]\n<\/pre>\n<p>tal que (interseccion xss) es la intersecci\u00f3n de la lista no vac\u00eda de listas infinitas crecientes xss; es decir, la lista de los elementos que pertenecen a todas las listas de xss. Por ejemplo,<\/p>\n<pre lang=\"text\">\n   \u03bb> take 10 (interseccion [[2,4..],[3,6..],[5,10..]])\n   [30,60,90,120,150,180,210,240,270,300]\n   \u03bb> take 10 (interseccion [[2,5..],[3,5..],[5,7..]])\n   [5,11,17,23,29,35,41,47,53,59]\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\n-- 1\u00aa soluci\u00f3n\n-- ===========\n\ninterseccion :: Ord a => [[a]] -> [a]\ninterseccion [xs]        = xs\ninterseccion (xs:ys:zss) = interseccionDos xs (interseccion (ys:zss))\n\ninterseccionDos :: Ord a => [a] -> [a] -> [a]\ninterseccionDos (x:xs) (y:ys)\n  | x == y    = x : interseccionDos xs ys\n  | x < y     = interseccionDos (dropWhile (<y) xs) (y:ys)\n  | otherwise = interseccionDos (x:xs) (dropWhile (<x) ys)  \n\n-- 2\u00aa soluci\u00f3n\n-- ===========\n\ninterseccion2 :: Ord a => [[a]] -> [a]\ninterseccion2 = foldl1 interseccionDos\n\n-- 3\u00aa soluci\u00f3n\n-- ===========\n\ninterseccion3 :: Ord a => [[a]] -> [a]\ninterseccion3 (xs:xss) =\n  [x | x <- xs, all (x `pertenece`) xss]\n \npertenece :: Ord a => a -> [a] -> Bool\npertenece x xs = x == head (dropWhile (<x) xs)\n<\/pre>\n<h4>Pensamiento<\/h4>\n<blockquote><p>\nDios no es el creador del mundo (seg\u00fan Mart\u00edn), sino el creador de la nada.<\/p>\n<p>Antonio Machado\n<\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"<p>Definir la funci\u00f3n interseccion :: Ord a => [[a]] -> [a] tal que (interseccion xss) es la intersecci\u00f3n de la lista no vac\u00eda de listas infinitas crecientes xss; es decir, la lista de los elementos que pertenecen a todas las listas de xss. Por ejemplo, \u03bb> take 10 (interseccion [[2,4..],[3,6..],[5,10..]]) [30,60,90,120,150,180,210,240,270,300] \u03bb> take 10 (interseccion&#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":[7],"tags":[59,359,415,11,6],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/5256"}],"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=5256"}],"version-history":[{"count":3,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/5256\/revisions"}],"predecessor-version":[{"id":5296,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/5256\/revisions\/5296"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=5256"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=5256"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=5256"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}