算法设计与分析课

今天上算法设计与分析课，第一节，里面看到了求集合幂集与集合全排列的问题，觉得用Haskell应该很容易实现，就写了这两个程序

 

setPower :: [a] -> [[a]] 

setPower xs = powerSet xs [[]]

 

powerofSet :: [a] -> [[a]] -> [[a]]

powerofSet  []  ys    = ys 

powerofSet  (x:xs) ys = powerSet xs (ys ++ map ((:) x) ys)

 

arrange :: (Ord a) => [a] -> [[a]]

arrange []   = [[]]

arrange xs   =  [  x | y <- (map (/x -> map ((:) x) $ arrange (xs // [x])) xs), x <- y]