{"id":3454,"date":"2017-11-30T06:00:16","date_gmt":"2017-11-30T04:00:16","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=3454"},"modified":"2017-12-08T08:29:38","modified_gmt":"2017-12-08T06:29:38","slug":"expresiones-equilibradas","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/expresiones-equilibradas\/","title":{"rendered":"Expresiones equilibradas"},"content":{"rendered":"<p>Una cadena de par\u00e9ntesis abiertos y cerrados est\u00e1 equilibrada si a cada par\u00e9ntesis abierto le corresponde uno cerrado y los restantes est\u00e1n equilibrados. Por ejemplo, \u00ab(()())\u00bb est\u00e1 equilibrada, pero \u00ab())(()\u00bb no lo est\u00e1.<\/p>\n<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   equilibrada :: String -> Bool\n<\/pre>\n<p>tal que (equilibrada cs) se verifica si la cadena cs est\u00e1 equilibrada. Por ejemplo,<\/p>\n<pre lang=\"text\">\n   equilibrada \"(()())\"          ==  True\n   equilibrada \"())(()\"          ==  False\n   equilibrada \"()\"              ==  True\n   equilibrada \")(()))\"          ==  False\n   equilibrada \"(\"               ==  False\n   equilibrada \"(())((()())())\"  == True\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\nimport Data.List (foldl')\nimport Test.Hspec\n\n-- 1\u00aa definici\u00f3n\nequilibrada :: String -> Bool\nequilibrada = aux 0 where\n  aux 0 []       = True\n  aux n ('(':cs) = aux (n + 1) cs \n  aux n (')':cs) = n > 0 && aux (n - 1) cs \n  aux _ _        = False\n\n-- 2\u00aa definici\u00f3n\nequilibrada2 :: String -> Bool\nequilibrada2 = aux 0 where\n  aux n []       = n == 0\n  aux n ('(':ps) = aux (n+1) ps\n  aux n (')':ps) = n > 0 && aux (n-1) ps\n\n-- 3\u00aa definici\u00f3n\nequilibrada3 :: String -> Bool\nequilibrada3 xs = null $ foldl' op [] xs where\n  op ('(':xs) ')' = xs\n  op xs x = x:xs\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Una cadena de par\u00e9ntesis abiertos y cerrados est\u00e1 equilibrada si a cada par\u00e9ntesis abierto le corresponde uno cerrado y los restantes est\u00e1n equilibrados. Por ejemplo, \u00ab(()())\u00bb est\u00e1 equilibrada, pero \u00ab())(()\u00bb no lo est\u00e1. Definir la funci\u00f3n equilibrada :: String -> Bool tal que (equilibrada cs) se verifica si la cadena cs est\u00e1 equilibrada. Por ejemplo,&#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":[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\/3454"}],"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=3454"}],"version-history":[{"count":3,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/3454\/revisions"}],"predecessor-version":[{"id":3502,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/3454\/revisions\/3502"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=3454"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=3454"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=3454"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}