{"id":6810,"date":"2022-03-24T06:00:50","date_gmt":"2022-03-24T04:00:50","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=6810"},"modified":"2022-03-31T18:59:33","modified_gmt":"2022-03-31T16:59:33","slug":"elemento-mas-repetido-de-manera-consecutiva","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/elemento-mas-repetido-de-manera-consecutiva\/","title":{"rendered":"Elemento m\u00e1s repetido de manera consecutiva"},"content":{"rendered":"

Definir la funci\u00f3n<\/p>\n

\n   masRepetido :: Ord a => [a] -> (a,Int)\n<\/pre>\n
tal que (masRepetido xs)<\/code> es el elemento de xs<\/code> que aparece m\u00e1s veces de manera consecutiva en la lista junto con el n\u00famero de sus apariciones consecutivas; en caso de empate, se devuelve el mayor de dichos elementos. Por ejemplo,<\/p>\n
\n   masRepetido [1,1,4,4,1]  ==  (4,2)\n   masRepetido [4,4,1,1,5]  ==  (4,2)\n   masRepetido \"aadda\"      ==  ('d',2)\n   masRepetido \"ddaab\"      ==  ('d',2)\n   masRepetido (show (product [1..5*10^4]))  ==  ('0',12499)\n<\/pre>\n
Soluciones<\/h4>\n
\nimport Data.List (group)\nimport Data.Tuple (swap)\nimport Control.Arrow ((&&&))\nimport Test.QuickCheck\n\n-- 1\u00aa soluci\u00f3n\n-- ===========\n\nmasRepetido1 :: Ord a => [a] -> (a,Int)\nmasRepetido1 [x] = (x,1)\nmasRepetido1 (x:y:zs) | m > n      = (x,m)\n                      | m == n     = (max x u,m)\n                      | otherwise  = (u,n)\n  where (u,n)  = masRepetido1 (y:zs)\n        m      = length (takeWhile (==x) (x:y:zs))\n\n-- 2\u00aa soluci\u00f3n\n-- ===========\n\nmasRepetido2 :: Ord a => [a] -> (a,Int)\nmasRepetido2 (x:xs)\n  | null xs'   = (x,length (x:xs))\n  | m > n      = (x,m)\n  | m == n     = (max x u,m)\n  | otherwise  = (u,n)\n  where xs'    = dropWhile (== x) xs\n        m      = length (takeWhile (==x) (x:xs))\n        (u,n)  = masRepetido2 xs'\n\n-- 3\u00aa soluci\u00f3n\n-- ===========\n\nmasRepetido3 :: Ord a => [a] -> (a,Int)\nmasRepetido3 xs = (n,z)\n  where (z,n) = maximum [(1 + length ys,y) | (y:ys) <- group xs]\n\n-- 4\u00aa soluci\u00f3n\n-- ============\n\nmasRepetido4 :: Ord a => [a] -> (a,Int)\nmasRepetido4 xs =\n  swap (maximum [(1 + length ys,y) | (y:ys) <- group xs])\n\n-- 5\u00aa soluci\u00f3n\n-- ============\n\nmasRepetido5 :: Ord a => [a] -> (a,Int)\nmasRepetido5 xs =\n  swap (maximum (map (\\ys -> (length ys, head ys)) (group xs)))\n\n-- 6\u00aa soluci\u00f3n\n-- ============\n\nmasRepetido6 :: Ord a => [a] -> (a,Int)\nmasRepetido6 =\n  swap . maximum . map ((,) <$> length <*> head) . group\n\n-- 7\u00aa soluci\u00f3n\n-- ============\n\nmasRepetido7 :: Ord a => [a] -> (a,Int)\nmasRepetido7 =\n  swap . maximum . map (length &&& head) . group\n\n-- Comprobaci\u00f3n de equivalencia\n-- ============================\n\n-- La propiedad es\nprop_masRepetido :: NonEmptyList Int -> Bool\nprop_masRepetido (NonEmpty xs) =\n  all (== masRepetido1 xs)\n      [masRepetido2 xs,\n       masRepetido3 xs,\n       masRepetido4 xs,\n       masRepetido5 xs,\n       masRepetido6 xs,\n       masRepetido7 xs]\n\n-- La comprobaci\u00f3n es\n--    \u03bb> quickCheck prop_masRepetido\n--    +++ OK, passed 100 tests.\n\n-- Comparaci\u00f3n de eficiencia\n-- =========================\n\n-- La comparaci\u00f3n es\n--    \u03bb> masRepetido1 (show (product [1..3*10^4]))\n--    ('0',7498)\n--    (3.72 secs, 2,589,930,952 bytes)\n--    \u03bb> masRepetido2 (show (product [1..3*10^4]))\n--    ('0',7498)\n--    (1.27 secs, 991,406,232 bytes)\n--    \u03bb> masRepetido3 (show (product [1..3*10^4]))\n--    ('0',7498)\n--    (0.85 secs, 945,399,976 bytes)\n--    \u03bb> masRepetido4 (show (product [1..3*10^4]))\n--    ('0',7498)\n--    (0.86 secs, 945,399,888 bytes)\n--    \u03bb> masRepetido5 (show (product [1..3*10^4]))\n--    ('0',7498)\n--    (0.80 secs, 943,760,760 bytes)\n--    \u03bb> masRepetido6 (show (product [1..3*10^4]))\n--    ('0',7498)\n--    (0.78 secs, 945,400,400 bytes)\n--    \u03bb> masRepetido7 (show (product [1..3*10^4]))\n--    ('0',7498)\n--    (0.78 secs, 942,122,088 bytes)\n--\n--    \u03bb> masRepetido2 (show (product [1..5*10^4]))\n--    ('0',12499)\n--    (3.27 secs, 2,798,156,008 bytes)\n--    \u03bb> masRepetido3 (show (product [1..5*10^4]))\n--    ('0',12499)\n--    (2.20 secs, 2,716,952,408 bytes)\n--    \u03bb> masRepetido4 (show (product [1..5*10^4]))\n--    ('0',12499)\n--    (2.22 secs, 2,716,952,320 bytes)\n--    \u03bb> masRepetido5 (show (product [1..5*10^4]))\n--    ('0',12499)\n--    (2.18 secs, 2,714,062,328 bytes)\n--    \u03bb> masRepetido6 (show (product [1..5*10^4]))\n--    ('0',12499)\n--    (2.17 secs, 2,716,952,832 bytes)\n--    \u03bb> masRepetido7 (show (product [1..5*10^4]))\n--    ('0',12499)\n--    (2.17 secs, 2,711,172,792 bytes)\n<\/pre>\n
El c\u00f3digo se encuentra en GitHub<\/a>.<\/p>\n
La elaboraci\u00f3n de las soluciones se describe en el siguiente v\u00eddeo<\/p>\n