字符串的排列，Haskell

Question

我有一个给定的字符串：abcdpqrs，其中输出为：badcqpsr。

我目前的代码：

f :: [a] -> [a]
f (a:b:xs) = b:a:xs
f xs = xs

评估f "abcdpqrs"结果为"bacdpqrs"。如何用它来获得＆＃34; badcqpsr＆＃34;？

Answer 1

通过递归列表的其余部分，尝试处理的不仅仅是前两个字符：

f :: [a] -> [a]
f (a:b:xs) = b:a:f xs
f xs = xs