Compress a Sequence – Rich 4Clojure Problem 30 – See: https://github.com/PEZ/rich4clojure

rich4clojure_easy_problem_030.clj

(ns rich4clojure.easy.problem-030
  (:require [hyperfiddle.rcf :refer [tests]]))

;; = Compress a Sequence =
;; By 4Clojure user: dbyrne
;; Difficulty: Easy
;; Tags: [seqs]
;; 
;; Write a function which removes consecutive duplicates
;; from a sequence.

(def __ :tests-will-fail)

(comment
  
  )

(tests
  (apply str (__ "Leeeeeerrroyyy")) := "Leroy"
  (__ [1 1 2 3 3 2 2 3]) := '(1 2 3 2 3)
  (__ [[1 2] [1 2] [3 4] [1 2]]) := '([1 2] [3 4] [1 2]))

;; To participate, fork:
;; https://github.com/PEZ/rich4clojure

;; Post your solution below, please!

(fn [s]
          (loop [prev-char (first s)
                 current-char (second s)
                 s (nthrest s 2)
                 result [prev-char]]
            (if (empty? s)
              (if (= prev-char current-char)
                result
                (conj result current-char))
                (if (= prev-char current-char)
                  (recur prev-char (first s) (rest s) result)
                  (recur current-char (first s) (rest s) (conj result current-char))))))

(defn dedup
  [s]
  (if (empty? s)
    '()
    (cons (first s)
          (->> s
               (partition 2 1)
               (filter #(not= (first %) (second %)))
               (map second)))))

(def __ dedup)

(def __ #(map first (partition-by
identity %)))

with some reference to ClojureDocs.

(def __ #(loop [l (seq %)
                res []]
           (if (empty? l)
             (seq res)
             (if (and (not-empty res) (= (last res) (first l)))
               (recur (rest l) res)
               (recur (rest l) (conj res (first l)))))))

  (defn __ [l]
    (filter some?
            (map-indexed
             (fn [idx value] (if (not= value (get l (+ idx 1))) value)) l)))

(def __ (fn [s]
          (->> s
               (reduce
                (fn [acc curr]
                  (if (= (last acc) curr)
                    acc
                    (concat acc (list curr))))
                (list)))))

(defn consecutive-duplicates [coll]
  (partition-by identity coll))

(defn get-firsts [coll]
  (map first coll))

(def __ #(-> % consecutive-duplicates get-firsts))