这是一种算法,让你在线排序:
它是没有效率的,但它是够懒,让您转到不同的排序几代人,即使你排序无限列表。这是一个很好的噱头,但不是很有用。例如,排序无限列表[10,9 ..]:
*Main> take 10 $ sortingStream [10,9..] !! 0
[9,8,7,6,5,4,3,2,1,0]
*Main> take 10 $ sortingStream [10,9..] !! 1
[8,7,6,5,4,3,2,1,0,-1]
*Main> take 10 $ sortingStream [10,9..] !! 2
[7,6,5,4,3,2,1,0,-1,-2]
*Main> take 10 $ sortingStream [10,9..] !! 3
[6,5,4,3,2,1,0,-1,-2,-3]
*Main> take 10 $ sortingStream [10,9..] !! 4
[5,4,3,2,1,0,-1,-2,-3,-4]
*Main> take 10 $ sortingStream [10,9..] !! 1000
[-991,-992,-993,-994,-995,-996,-997,-998,-999,-1000]
正如您所看到的排序改进了每一代。代码:
produce :: ([a] -> [a]) -> [a] -> [[a]]
produce f xs = f xs : (produce f (f xs))
sortingStream :: (Ord a) => [a] -> [[a]]
sortingStream = produce ss
ss :: (Ord a) => [a] -> [a]
ss [] = []
ss [x] = [x]
ss [x,y] | x <= y = [x,y]
| otherwise = [y,x]
ss (x:y:xs) | x <= y = x: (ss (y:xs))
| otherwise = y:(ss (x:xs))
你能保证输入列表按照你的例子排序吗? – 2010-03-07 00:52:39