Interleave Two Seqs – Rich 4Clojure Problem 39 – See: https://github.com/PEZ/rich4clojure

rich4clojure_easy_problem_039.clj

(ns rich4clojure.easy.problem-039
  (:require [hyperfiddle.rcf :refer [tests]]))

;; = Interleave Two Seqs =
;; By 4Clojure user: dbyrne
;; Difficulty: Easy
;; Tags: [seqs core-functions]
;; 
;; Write a function which takes two sequences and returns
;; the first item from each, then the second item from
;; each, then the third, etc.

(def restricted [interleave])

(def __ :tests-will-fail)

(comment
  
  )

(tests
  (__ [1 2 3] [:a :b :c]) := '(1 :a 2 :b 3 :c)
  (__ [1 2] [3 4 5 6]) := '(1 3 2 4)
  (__ [1 2 3 4] [5]) := [1 5]
  (__ [30 20] [25 15]) := [30 25 20 15])

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

;; Post your solution below, please!

(def __ #(loop [a %1
               b %2
               res []]
          (if (or (empty? a) (empty? b))
            res
            (recur (rest a)
                   (rest b)
                   (conj (conj res (first a)) (first b))))))

(defn my-interleave
  [[frst1 & rst1] [frst2 & rst2]]
  (when (and frst1 frst2)
    (lazy-seq
     (concat [frst1 frst2] (my-interleave rst1 rst2)))))

(def __ my-interleave)

(defn __ [xs ys]
  (mapcat vector xs ys))

(fn [seq1 seq2]
(mapcat #(list %1 %2)
seq1 seq2) )

(def __
  (fn [& colls]
    (loop [cs colls
           acc []]
      (if
       ;; are any of the colls empty?
       (seq (filter (fn [c] (not (seq c))) cs))
        acc
        (recur (map rest cs) (into acc (map first cs)))))))

defined to handle & colls, rather than just 2 colls

(defn __
  ([c1 c2] (__ [] c1 c2))
  ([acc [h1 & t1] [h2 & t2]]
   (if (or (nil? h1) (nil? h2))
     acc
     (recur (conj acc h1 h2) t1 t2))))