my take on this problem http://siscia.github.io/2013/07/21/algorithm-problem-for-job

zerosum.clj

(defn can-sum-to-zero
  ([nums]
     (can-zero nums #{}))
  ([nums can-sum-to]
     (when (seq nums)
       (let [num (first nums)]
         (if (can-sum-to (- num))
           true
           (let [can-also-sum-to (map #(+ num %) can-sum-to)]
             (recur (rest nums)
                    (clojure.set/union can-sum-to can-also-sum-to #{num}))))))))

This approach is a breadth first search of all the possible sums you can reach starting from the beginning of the list. It has the advantage of being able to prune subsets that sum to the same value, but since it does need to keep all the sums it can require more memory