{"id":2687,"date":"2016-12-13T06:00:39","date_gmt":"2016-12-13T04:00:39","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=2687"},"modified":"2016-12-20T07:22:59","modified_gmt":"2016-12-20T05:22:59","slug":"agrupacion-por-orden-de-aparicion","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/agrupacion-por-orden-de-aparicion\/","title":{"rendered":"Agrupaci\u00f3n por orden de aparici\u00f3n"},"content":{"rendered":"<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   agrupacion :: Eq a => [a] -> [a]\n<\/pre>\n<p>tal que (agrupacion xs) es la lista obtenida agrupando los elementos de xs seg\u00fan su primera aparici\u00f3n. Por ejemplo,<\/p>\n<pre lang=\"text\">\n   agrupacion [3,1,5,1,7,1,5,3]  ==  [3,3,1,1,1,5,5,7]\n   agrupacion \"babcacb\"          ==  \"bbbaacc\"\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\nimport Data.List (nub, partition)\n\n-- 1\u00aa definici\u00f3n\nagrupacion :: Eq a => [a] -> [a]\nagrupacion [] = []\nagrupacion (x:xs) =\n  x : filter (==x) xs ++ agrupacion (filter (\/=x) xs)\n\n-- 2\u00aa definici\u00f3n\nagrupacion2 :: Eq a => [a] -> [a]\nagrupacion2 xs = concat [filter (x==) xs | x <- nub xs]\n\n-- 3\u00aa definici\u00f3n\nagrupacion3 :: Eq a => [a] -> [a]\nagrupacion3 []     = []\nagrupacion3 (x:xs) = x : ys ++ agrupacion3 zs\n  where (ys,zs) = partition (==x) xs\n\n-- Comparaci\u00f3n de eficiencia\n--    \u03bb> import Data.List (cycle)\n--    \u03bb> :set +s\n--    \u03bb> sum (agrupacion (take (10^7) (cycle [0,1,2,3])))\n--    15000000\n--    (24.40 secs, 3,173,123,368 bytes)\n--    \u03bb> sum (agrupacion2 (take (10^7) (cycle [0,1,2,3])))\n--    15000000\n--    (13.71 secs, 2,333,129,416 bytes)\n--    \u03bb> sum (agrupacion3 (take (10^7) (cycle [0,1,2,3])))\n--    15000000\n--    (22.33 secs, 5,080,127,944 bytes)\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Definir la funci\u00f3n agrupacion :: Eq a => [a] -> [a] tal que (agrupacion xs) es la lista obtenida agrupando los elementos de xs seg\u00fan su primera aparici\u00f3n. Por ejemplo, agrupacion [3,1,5,1,7,1,5,3] == [3,3,1,1,1,5,5,7] agrupacion \u00abbabcacb\u00bb == \u00abbbbaacc\u00bb Soluciones import Data.List (nub, partition) &#8212; 1\u00aa definici\u00f3n agrupacion :: Eq a => [a] -> [a] agrupacion&#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":[12,38,24,11,339,6],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2687"}],"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=2687"}],"version-history":[{"count":5,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2687\/revisions"}],"predecessor-version":[{"id":2717,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2687\/revisions\/2717"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=2687"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=2687"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=2687"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}