99-Problems-In-Clojure.clj

;; P01
(last [1 1 2 3 5 8])

;; P02
(defn penultimate [x]
  (last (butlast x)) )

;; P03
(nth [1 1 2 3 5 8] 2)

;; P04
(count [1 1 2 3 5 8])

;; P05
(reverse [1 1 2 3 5 8])

;; P06
(defn palindrome? [x]
  (= x (reverse x)) )

;; P07
(flatten [[1 1] 2 [3 [5 8]]])

;; P08
(defn compress [x]
  (map first (partition-by identity x)) )

;; P09
(defn pack [x]
  (partition-by identity x) )

;; P10
(defn encode [x]
  (map #(list (count %) (first %))
       (pack x)) )

;; P11
(defn encode-modified [x]
  (map #(if (<= (count %) 1) % (list (count %) (first %)))
       (pack x)) )

;; P12
(defn decode [x]
  (mapcat #(repeat (first %) (second %)) x) )

;; P13
;; Not sure what this problem is trying to specify

;; P14
(defn duplicate [x]
  (interleave x x) )

;; P15
(defn duplicate-n [n x]
  (mapcat #(repeat n %) x) )

;; P16
(defn drop-nth [n coll]
  (lazy-seq
    (when-let [xs (seq coll)]
      (concat (take (dec n) xs) (drop-nth n (drop n xs)))
    )
  )
)

;; P17
(split-at 3 "abcdefghij")

;; P19
(defn rotate [n coll]
  (let [r (if (not (neg? n)) n (+ n (count coll)))]
    (concat (drop r coll) (take r coll)) ) )