Question

示例：split [1;3;2;4;7;9];;
输出：([1;3;7;9], [2;4])

我是F＃的新手，我无法弄明白无法使用partition内置功能。</ p>

这是我到目前为止所做的：

let rec split xs = 
    match xs with
    | [] -> [], []
    | xs -> xs, []
    | xh::xt -> let odds, evens = split xt
                if (xh % 2) = 0 then xh::odds, xh::evens
                else xh::odds, evens

固定代码：

let rec split xs = 
    match xs with
    | [] -> [], []
    | xh::xt -> let odds, evens = split xt
                if (xh % 2) = 0 then odds, xh::evens
                else xh::odds, evens

*感谢@TheInnerLight指出我的错误：无法访问的案例和不必要的修改赔率

Answer 1

您可以使用内置的List.partition功能

let splitOddEven xs =
    xs |> List.partition (fun x -> x % 2 <> 0)

splitOddEven [1;3;2;4;7;9];;
val it : int list * int list = ([1; 3; 7; 9], [2; 4])

如果你想要一个递归实现，我可能会采用这样的尾递归实现：

let splitOddEven xs =
    let rec splitOddEvenRec oddAcc evenAcc xs = 
        match xs with
        | [] -> oddAcc, evenAcc
        | xh::xt -> 
            if (xh % 2) = 0 then splitOddEvenRec oddAcc (xh :: evenAcc) xt
            else splitOddEvenRec (xh :: oddAcc) evenAcc xt
    splitOddEvenRec [] [] xs

splitOddEven  [1;3;2;4;7;9]

请注意，这将以相反的顺序为您提供两个结果列表，因此您可能希望自己反转它们。

F＃ - 将列表拆分为奇偶列表的元组（按元素，而不是位置）

1 个答案: