Definir la funci\u00f3n<\/p>\n
\n solitario :: Ord a => [a] -> a\n<\/pre>\ntal que (solitario xs) es el \u00fanico elemento que ocurre una vez en la lista xs (se supone que la lista xs tiene al menos 3 elementos y todos son iguales menos uno que es el solitario). Por ejemplo,<\/p>\n
\n solitario [2,2,7,2] == 7\n solitario [2,2,2,7] == 7\n solitario [7,2,2,2] == 7\n solitario (replicate (2*10^7) 1 ++ [2]) == 2\n<\/pre>\nSoluciones<\/h4>\n\nimport Test.QuickCheck \nimport Data.List (group, nub, sort)\n\n-- 1\u00aa definici\u00f3n\n-- =============\n\nsolitario :: Ord a => [a] -> a\nsolitario xs =\n head [x | x <- xs\n , cuenta xs x == 1]\n\ncuenta :: Eq a => [a] -> a -> Int\ncuenta xs x = length [y | y <- xs\n , x == y]\n\n-- 2\u00aa definici\u00f3n\n-- =============\n\nsolitario2 :: Ord a => [a] -> a\nsolitario2 xs = head (filter (\\x -> cuenta2 xs x == 1) xs)\n\ncuenta2 :: Eq a => [a] -> a -> Int\ncuenta2 xs x = length (filter (==x) xs)\n\n-- 3\u00aa definici\u00f3n\n-- =============\n\nsolitario3 :: Ord a => [a] -> a\nsolitario3 [x] = x\nsolitario3 (x1:x2:x3:xs)\n | x1 \/= x2 && x2 == x3 = x1\n | x1 == x2 && x2 \/= x3 = x3\n | otherwise = solitario3 (x2:x3:xs)\n\n-- 4\u00aa definici\u00f3n\n-- =============\n\nsolitario4 :: Ord a => [a] -> a\nsolitario4 xs \n | y1 == y2 = last ys\n | otherwise = y1\n where (y1:y2:ys) = sort xs\n\n-- 5\u00aa definici\u00f3n\n-- =============\n\nsolitario5 :: Ord a => [a] -> a\nsolitario5 xs | null ys = y\n | otherwise = z\n where [y:ys,z:zs] = group (sort xs)\n\n-- 6\u00aa definici\u00f3n\n-- =============\n\nsolitario6 :: Ord a => [a] -> a\nsolitario6 xs =\n head [x | x <- nub xs\n , cuenta xs x == 1]\n\n-- 7\u00aa definici\u00f3n\n-- =============\n\nsolitario7 :: Ord a => [a] -> a\nsolitario7 (a:b:xs)\n | a == b = solitario7 (b:xs)\n | elem a (b:xs) = b\n | elem b (a:xs) = a\nsolitario7 [a,b] = b\n\n-- Equivalencia\n-- ============\n\n-- Propiedad de equivalencia\nprop_solitario_equiv :: Property\nprop_solitario_equiv =\n forAll listaSolitaria (\\xs -> solitario xs == solitario2 xs &&\n solitario xs == solitario3 xs &&\n solitario xs == solitario4 xs &&\n solitario xs == solitario5 xs &&\n solitario xs == solitario6 xs &&\n solitario xs == solitario7 xs)\n\n-- Generador de listas con al menos 3 elementos y todos iguales menos\n-- uno. Por ejemplo,\n-- \u03bb> sample listaSolitaria\n-- [1,0,0,0,0]\n-- [0,0,-1,0,0,0]\n-- [4,1,1,1]\n-- [6,6,4,6]\n-- [8,8,8,8,8,-4,8,8,8,8,8,8]\n-- ...\nlistaSolitaria :: Gen [Int]\nlistaSolitaria = do\n n <- arbitrary\n m <- arbitrary `suchThat` (\\a -> n + a > 2)\n x <- arbitrary\n y <- arbitrary `suchThat` (\\a -> a \/= x)\n return (replicate n x ++ [y] ++ replicate m x)\n\n-- Comprobaci\u00f3n:\n-- \u03bb> quickCheck prop_solitario_equiv\n-- +++ OK, passed 100 tests.\n\n-- Comparaci\u00f3n de eficiencia:\n-- \u03bb> solitario (replicate (5*10^3) 1 ++ [2])\n-- 2\n-- (5.47 secs, 3,202,688,152 bytes)\n-- \u03bb> solitario2 (replicate (5*10^3) 1 ++ [2])\n-- 2\n-- (2.08 secs, 1,401,603,960 bytes)\n-- \u03bb> solitario3 (replicate (5*10^3) 1 ++ [2])\n-- 2\n-- (0.04 secs, 3,842,240 bytes)\n-- \u03bb> solitario4 (replicate (5*10^3) 1 ++ [2])\n-- 2\n-- (0.02 secs, 1,566,472 bytes)\n-- \u03bb> solitario5 (replicate (5*10^3) 1 ++ [2])\n-- 2\n-- (0.01 secs, 927,064 bytes)\n-- \u03bb> solitario6 (replicate (5*10^3) 1 ++ [2])\n-- 2\n-- (0.01 secs, 1,604,176 bytes)\n-- \u03bb> solitario7 (replicate (5*10^3) 1 ++ [2])\n-- 2\n-- (0.01 secs, 1,923,440 bytes)\n-- \n-- \u03bb> solitario3 (replicate (5*10^6) 1 ++ [2])\n-- 2\n-- (4.62 secs, 3,720,123,560 bytes)\n-- \u03bb> solitario4 (replicate (5*10^6) 1 ++ [2])\n-- 2\n-- (1.48 secs, 1,440,124,240 bytes)\n-- \u03bb> solitario5 (replicate (5*10^6) 1 ++ [2])\n-- 2\n-- (1.40 secs, 1,440,125,936 bytes)\n-- \u03bb> solitario6 (replicate (5*10^6) 1 ++ [2])\n-- 2\n-- (2.65 secs, 1,480,125,032 bytes)\n-- \u03bb> solitario7 (replicate (5*10^6) 1 ++ [2])\n-- 2\n-- (2.21 secs, 1,800,126,224 bytes)\n-- \n-- \u03bb> solitario5 (2 : replicate (5*10^6) 1)\n-- 2\n-- (1.38 secs, 1,520,127,864 bytes)\n-- \u03bb> solitario6 (2 : replicate (5*10^6) 1)\n-- 2\n-- (1.18 secs, 560,127,664 bytes)\n-- \u03bb> solitario7 (2 : replicate (5*10^6) 1)\n-- 2\n-- (0.29 secs, 280,126,888 bytes)\n<\/pre>\nPensamiento<\/h4>\n\nSube y sube, pero ten
\ncuidado Nefelibata,
\nque entre las nubes tambi\u00e9n,
\nse puede meter la pata.<\/p>\n
Antonio Machado\n<\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"
Definir la funci\u00f3n solitario :: Ord a => [a] -> a tal que (solitario xs) es el \u00fanico elemento que ocurre una vez en la lista xs (se supone que la lista xs tiene al menos 3 elementos y todos son iguales menos uno que es el solitario). Por ejemplo, solitario [2,2,7,2] == 7 solitario…<\/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":[8,38,13,71,134,28,141,11,6,14],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/4343"}],"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=4343"}],"version-history":[{"count":5,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/4343\/revisions"}],"predecessor-version":[{"id":4591,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/4343\/revisions\/4591"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=4343"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=4343"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=4343"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}