我最近为F#项目编写了以下组合和排列函数,但我很清楚它们远未优化.
/// Rotates a list by one place forward.
let rotate lst =
List.tail lst @ [List.head lst]
/// Gets all rotations of a list.
let getRotations lst =
let rec getAll lst i = if i = 0 then [] else lst :: (getAll (rotate lst) (i - 1))
getAll lst (List.length lst)
/// Gets all permutations (without repetition) of specified length from a list.
let rec getPerms n lst =
match n, lst with
| 0, _ -> …