Weekly coding interview problem (https://www.interviewcake.com/free-weekly-coding-interview-problem-newsletter)

problem

You have an array of integers, and for each index you want to find the product of every integer except the integer at that index.

Write a function get_products_of_all_ints_except_at_index() that takes an array of integers and returns an array of the products.

For example, given:

  [1, 7, 3, 4]

your function would return:

  [84, 12, 28, 21]

by calculating:

  [7*3*4, 1*3*4, 1*7*4, 1*7*3]

solutions.clj

;; First solution that came to my mind ...

(defn get-products-of-all-ints-except-at-index
  [ints]
  (loop [ints ints
         processed []
         products []]
    (if (empty? ints)
      products
      (let [xs (rest ints)
            product (apply * (concat processed xs))]
        (recur xs
               (conj processed (first ints))
               (conj products product))))))

;; A cleaner solution by @mishadoff

(defn get-products-of-all-ints-except-at-index [ints]
  (map-indexed (fn [i _]
                 (->> ints
                      (keep-indexed (fn [j e] (when (not= i j) e)))
                      (reduce *)))
                 
  ints))