{"id":3513,"date":"2017-12-11T06:00:44","date_gmt":"2017-12-11T04:00:44","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=3513"},"modified":"2017-12-19T07:09:41","modified_gmt":"2017-12-19T05:09:41","slug":"numero-de-viajeros-en-el-autobus","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/numero-de-viajeros-en-el-autobus\/","title":{"rendered":"N\u00famero de viajeros en el autob\u00fas"},"content":{"rendered":"<p>Un autob\u00fas inicia su recorrido con 0 viajeros. El n\u00famero de viajeros que se suben y bajan en cada parada se representa por un par (x,y) donde x es el n\u00famero de las que suben e y el de las que bajan. Un recorrido del autob\u00fas se representa por una lista de pares representando los n\u00fameros de viajeros que suben o bajan en cada parada.<\/p>\n<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   nViajerosEnBus :: [(Int, Int)] -> Int\n<\/pre>\n<p>tal que (nViajerosEnBus ps) es el n\u00famero de viajeros en el autob\u00fas tras el recorrido ps. Por ejemplo,<\/p>\n<pre lang=\"text\">\n  nViajerosEnBus []                                        ==  0\n  nViajerosEnBus [(10,0),(3,5),(5,8)]                      ==  5\n  nViajerosEnBus [(3,0),(9,1),(4,10),(12,2),(6,1),(7,10)]  ==  17\n  nViajerosEnBus [(3,0),(9,1),(4,8),(12,2),(6,1),(7,8)]    ==  21\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\nimport Data.List (foldl')\n\n-- 1\u00aa soluci\u00f3n (por comprensi\u00f3n)\nnViajerosEnBus1 :: [(Int, Int)] -> Int\nnViajerosEnBus1 ps = sum [a - b | (a,b) <- ps]\n\n-- 2\u00aa solucio\u0144 (por recursi\u00f3n)\nnViajerosEnBus2 :: [(Int, Int)] -> Int\nnViajerosEnBus2 []         = 0\nnViajerosEnBus2 ((a,b):ps) = a - b + nViajerosEnBus2 ps\n\n-- 3\u00aa soluci\u00f3n (por recursi\u00f3n con acumulador)\nnViajerosEnBus3 :: [(Int, Int)] -> Int\nnViajerosEnBus3 = aux 0\n  where aux n []         = n\n        aux n ((a,b):xs) = aux (n+a-b) xs\n\n-- 4\u00aa soluci\u00f3n (por plegado por la derecha):\nnViajerosEnBus4 :: [(Int, Int)] -> Int\nnViajerosEnBus4 = foldr (\\(a,b) n -> a-b+n) 0\n\n-- 5\u00aa soluci\u00f3n (por plegado por la derecha):\nnViajerosEnBus5 :: [(Int, Int)] -> Int\nnViajerosEnBus5 = foldl' (\\n (a,b) -> a-b+n) 0\n\n-- 6\u00aa soluci\u00f3n (con map)\nnViajerosEnBus6 :: [(Int, Int)] -> Int\nnViajerosEnBus6 xs = sum (map (\\(x,y) -> x-y) xs)\n\n-- 7\u00aa soluci\u00f3n (por composici\u00f3n y sin argumentos) \nnViajerosEnBus7 :: [(Int, Int)] -> Int\nnViajerosEnBus7 = sum . map (uncurry (-))\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Un autob\u00fas inicia su recorrido con 0 viajeros. El n\u00famero de viajeros que se suben y bajan en cada parada se representa por un par (x,y) donde x es el n\u00famero de las que suben e y el de las que bajan. Un recorrido del autob\u00fas se representa por una lista de pares representando los&#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":[5],"tags":[8,185,94,10,11,6,40,271],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/3513"}],"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=3513"}],"version-history":[{"count":2,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/3513\/revisions"}],"predecessor-version":[{"id":3546,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/3513\/revisions\/3546"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=3513"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=3513"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=3513"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}