(defn rotate [a n]
(let [l (count a)
off (mod (+ (mod n l) l) l)]
(flatten (list (drop off a) (take off a)))))
(rotate '(1 2 3 4 5) -1) => (5 1 2 3 4)
(rotate '(1 2 3 4 5) -6) => (5 1 2 3 4)
(rotate '(1 2 3 4 5) 3) => (4 5 1 2 3)
(rotate '(1 2 3 4 5) 103) => (4 5 1 2 3)
(rotate '(1 2 3 4 5) 2) => (3 4 5 1 2)
(rotate '(1 2 3 4 5) 7) => (3 4 5 1 2)
Rotates any number of times
Handles zero with no conditional
n can be larger than the length and it will map correctly
Negative n rotates right, Positive n rotates left
On Thursday, April 22, 2010 at 9:13:52 AM UTC-6, Sean Devlin wrote:
>
> Oh wow... totally would have :)
>
> On Apr 21, 8:16 pm, Harvey Hirst <[email protected]> wrote:
> > > (defn rotate [n s]
> > > (let [[front back] (split-at (mod n (count s)) s)]
> > > (concat back front)))
> >
> > Don't forget (mod n 0) is an ArithmeticException.
> >
> > Harvey
> >
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