值列表中的組合列表？

Question

如何從列表中獲取組合列表？

例如：

ghci> getCombinations [[1,2,3],[10,20,30],[100,200,300]] 

[[1,10,100],[1,10,200],[1,10,300],[1,20,100],[1,20,200],[1,20,300],[1,30,100], 
[1,30,200],[1,30,300],[2,10,100],[2,10,200],[2,10,300],[2,20,100],[2,20,200], 
[2,20,300],[2,30,100],[2,30,200],[2,30,300],[3,10,100],[3,10,200],[3,10,300], 
[3,20,100],[3,20,200],[3,20,300],[3,30,100],[3,30,200],[3,30,300]] 

Answer 1

import Control.Applicative 

getCombinations :: [[a]] -> [[a]] 
getCombinations values = 
foldl (\acc values -> (\list value -> list ++ [value]) <$> acc <*> values) [[]] values 

getCombinations [[1,2,3],[10,20,30],[100,200,300]] 

[[1,10,100]，[1,10,200]，[1,10,300]，[1,20,100]，[1,20,200]，[1 ，20300]，[1,30,100]，[1,30,200]，[1,30,300]，[2,10,100]，[2,10,200]，[2,10,300]，[2,20,100]，[2,20,200 ]，[2,20,300]，[2,30,100]，[2,30,200]，[2,30,300]，[3,10,100]，[3,10,200]，[3,10,300]，[3,20,100] [3,20,200]，[3,20,300]，[3,30,100]，[3,30,200]，[3,30,300]]