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472 Eric Normand Newsletter

Roboto

A futuristic robot is programmed to take in a sequence of numbers. Each number is the distance to travel in a cardinal direction (north, south, east, west). It starts facing north at (0, 0), travels straight ahead by the distance given in the first number, then turns 90 degrees clockwise, now facing east. Then it repeats with the next number. Your job is to calculate where it ends up at the end of the sequence.

Examples

(move []) ;=> [0 0] ;; No motion
(move [10]) ;=> [0 10] ;; move 10 straight north
(move [10 2]) ;=> [2 10]
(move [10 2 3]) ;=> [2 7]

Thanks to this site for the problem idea, where it is rated Very Hard in Ruby. The problem has been modified.

Please submit your solutions as comments on this gist.

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@barrosfelipe
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Bit late to this party but here is mine:

(defn move [xs]
  (if-not (seq xs)
    [0 0]
    (->> xs
         (partition 4 4 [0 0 0 0])
         (apply #(map + %))
         ((fn [[a b c d]] [(- b d) (- a c)])))))

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