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00 sums of pairs.md

Sums of pairs

Write a function that takes a collection of numbers and a target number. Return all pairs of numbers found in the collection that sum up to the target number.

Examples

(sums-of-pairs [2 4 5 6] 8) ;=> [[2 6]]
(sums-of-pairs [3 2 0 1 1 5] 5) ;=> [[2 3] [0 5]]
(sums-of-pairs [1 3 2 3 4 5] 7) ;=> [[3 4] [3 4] [2 5]]

Notes

• There can be duplicate numbers.
• Each pair should be sorted.

Thanks to this site for the challenge idea where it is considered Expert level in JavaScript.

Please submit your solutions as comments on this gist.

Is it too late to answer? My solution to the problem-

(defn sums-of-pairs 
    [ns target] (first (reduce (fn [[l m] n]
                                   [(concat l (repeat (get m n 0) (sort [n (- target n)])))
                                    (update m (- target n) (fn [x] (if (= x nil) 1 (+ x 1))))]) [[] {}] ns)))
;; O(N) solution