{"id":358,"date":"2014-06-27T06:50:40","date_gmt":"2014-06-27T04:50:40","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=358"},"modified":"2014-11-29T12:21:12","modified_gmt":"2014-11-29T10:21:12","slug":"intercalacion-de-n-copias","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/intercalacion-de-n-copias\/","title":{"rendered":"Intercalaci\u00f3n de n copias"},"content":{"rendered":"<h4>Enunciado<\/h4>\n<pre lang=\"text\">\n-- Definir la funci\u00f3n \n--    intercala :: Int -> a -> [a] -> [[a]]\n-- tal que (intercala n x ys) es la lista de la listas obtenidas\n-- intercalando n copias de x en ys. Por ejemplo,\n--    intercala 2 'a' \"bc\" == [\"bcaa\",\"baca\",\"baac\",\"abca\",\"abac\",\"aabc\"]\n--    intercala 2 'a' \"c\"  == [\"caa\",\"aca\",\"aac\"]\n--    intercala 1 'a' \"c\"  == [\"ca\",\"ac\"]\n--    intercala 0 'a' \"c\"  == [\"c\"]\n-- Nota: No importa el orden de los elementos.\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\nimport Data.List \n\n-- 1\u00aa soluci\u00f3n\n-- ===========\n\nintercala1 :: Int -> a -> [a] -> [[a]]\nintercala1 0 _ xs     = [xs]\nintercala1 n y []     = [replicate n y]\nintercala1 n y (x:xs) = \n    concat [[replicate i y ++ (x:zs) | zs <- intercala1 (n-i) y xs]\n            | i <- [0..n]]\n\n-- 2\u00aa soluci\u00f3n\n-- ===========\n\nintercala2 :: Eq a => Int -> a -> [a] -> [[a]]\nintercala2 n x ys = nub (aux n x ys)\n    where \n      aux 0 _ ys = [ys]\n      aux n x ys = concat [intercalaUno x zs | zs <- aux (n-1) x ys]\n\n--    intercalaUno 'a' \"bc\"  == [\"abc\",\"bac\",\"bca\"]\nintercalaUno :: a -> [a] -> [[a]]\nintercalaUno x []     = [[x]]\nintercalaUno x (y:ys) = (x:y:ys) : [y:zs | zs <- intercalaUno x ys]\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Enunciado &#8212; Definir la funci\u00f3n &#8212; intercala :: Int -> a -> [a] -> [[a]] &#8212; tal que (intercala n x ys) es la lista de la listas obtenidas &#8212; intercalando n copias de x en ys. Por ejemplo, &#8212; intercala 2 &#8216;a&#8217; \u00abbc\u00bb == [\u00abbcaa\u00bb,\u00bbbaca\u00bb,\u00bbbaac\u00bb,\u00bbabca\u00bb,\u00bbabac\u00bb,\u00bbaabc\u00bb] &#8212; intercala 2 &#8216;a&#8217; \u00abc\u00bb == [\u00abcaa\u00bb,\u00bbaca\u00bb,\u00bbaac\u00bb] &#8212; intercala&#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":[4],"tags":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/358"}],"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=358"}],"version-history":[{"count":5,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/358\/revisions"}],"predecessor-version":[{"id":678,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/358\/revisions\/678"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=358"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=358"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=358"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}