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prajwalit/smallest-common-number.clj

Created September 1, 2011 17:36
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[4clojure #108] Given any number of sequences, each sorted from smallest to largest, find the smallest number which appears in each sequence. The sequences may be infinite, so be careful to search lazily.
Raw
smallest-common-number.clj
(defn smallest-common-number [& seqs]
(letfn [;; Get max of first items of seqs
(max-first [seqs]
(apply max (map first seqs)))
;; Test if first elemets are equal
(first-equal? [seqs]
(apply = (map first seqs)))
;; Filter values less than x
(update-seq [x coll]
(if (> x (first coll))
(update-seq x (rest coll))
coll))]
(let [curr (max-first seqs)]
(if (first-equal? seqs)
curr
(apply smallest-common-number (map #(update-seq curr %) seqs))))))
(smallest-common-number [1 2 3 4 5 12 18] [-1 5 10 12] [3 12 17])
;; => 12
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