我想我已经在 Haskell 中正确计算了Luhn 算法:
f1 :: Integer -> [Integer]
f1 x = if x < 10 then [x] else (f1 (div x 10))++[mod x 10]
f2 :: [Integer] -> [Integer]
f2 xs = [(!!) xs (x - 1) | x <- [1..(length xs)] , even x]
f3 :: [Integer] -> [Integer]
f3 xs = if mod (length xs) 2 /= 0 then (f2 xs) else (f2 (0:xs))
f4 :: [Integer] -> [Integer]
f4 xs = map (*2) (f3 xs)
f5 :: [Integer] -> [[Integer]]
f5 xs = map f1 xs
f6 :: [[Integer]] -> [Integer]
f6 [] = []
f6 (xs : xss) = xs++(f6 xss)
f7 :: [Integer] -> [Integer]
f7 xs = [(!!) xs (x - 1) | x <- [1..(length xs)] , odd x]
f8 :: [Integer] -> [Integer]
f8 xs = if mod (length xs) 2 /= 0 then (f7 xs) else (f7 (0:xs))
f9 :: [Integer] -> [Integer]
f9 xs = (f8 xs) ++ (f4 xs)
f :: Integer -> Integer
f x = sum (f6 (f5 (f9 xs)))
where xs = f1 x
luhn :: Integer -> Bool
luhn x = if mod (f x) 10 == 0 then True else False
例如,
luhn 49927398716 ==> True
luhn 49927398717 ==> False
现在我必须创建一个新函数sigLuhn
,这样,给定一个整数n
,luhn n == True
,然后sigLuhn n
给出一个数字(或多个数字),这样如果我们将数字添加到最后一个 to n
,那么新数字也可以验证 Luhn 算法;如果luhn n == False
函数给出错误。例如,
sigLuhn 49927398716 ==> [8]
因为如果我们n = 49927398716
打电话
luhn (10*n + 8) ==> True
是8
的最小整数0
。我的想法是下一个:
g1 :: Integer -> Integer
g1 x = div 10 x + 1
g2 :: Integer -> Integer -> Integer
g2 x y = x*(floor (10)^(g1 y)) + y
g3 :: Integer -> [Bool]
g3 x = [luhn (g2 x y) | y <- [1..]]
g4 :: [Bool] -> Int
g4 xs = minimum (elemIndices True xs)
g :: Integer -> Int
g x = g4 (g3 x)
sigLuhn :: Integer -> [Int]
sigLuhn x = if (luhn x) then [g x] else error "The conditions of Luhn's algorithm are not valid"
该代码没有给出错误,但sigLuhn
此代码不正确。简而言之,如果我们假设功能luhn
是好的,你能帮我写sigLuhn
正确吗?非常感谢。