Clojure Course - Introduction

Challenge 1987

Find two numbers with these characteristics:

They are prime numbers.
The last two digits are divisible by 3.
The sum of all digits is divisible by 5.
They are only 3 digits long.
Two clues: "ewstvno" and "egritnh".

Solution in Clojure language:


(defn prime? 
  "Check if a number is prime"
  [n]
  (let [divisors (cons 2 (range 3 (inc (Math/sqrt n)) 2))]
    (not-any? #(zero? (mod n %)) divisors)))

(defn divisible?
  "Is the number divisible by something?"
  [n divisor]
  (zero? (mod n divisor)))

(defn number->digits
  "Convert a number to a list of digits"
  [n] 
  (map js/parseInt (str n)))

(def letters
  (zipmap 
   (range 10) 
   ["zero" "one" "two" "three" "four"
    "five" "six" "seven" "eight" "nine"]))

(defn hash-number
  "Make a hash-set of letter from a number's digits"
  [n]
  (set (apply str (map letters (number->digits n)))))

(->> (range 100 1000)
  (filter prime?)
  (filter #(divisible? (apply + (number->digits %)) 5))
  (filter #(divisible? (mod % 100) 3))
  (filter #(contains? (set (map set ["ewstvno" "egritnh"])) 
    (hash-number %))))

Thank you, great challenge!

[clj] 1987 detective challenge