birthday.clj

(defn birthday-collision?
  "Generates a birthday (0-364) for person-count
   number of people. Returns a boolean value
   indicating whether there were two or more
   people with the same birthday."
  [person-count]
  (let [rand-days
        (for [x (range person-count)]
          (rand-int 365))]
    (let [matches (->> (frequencies rand-days)
                       (vals)
                       (filter #(> % 1)))]
      (not (empty? matches)))))
      
(defn run-simulation
  "Runs the birthday-collision? function
   iters number of iterations for person-count
   number of people. Prints a formatted result
   detailing the result of the simulation."
  [iters person-count]
  (let [results (for [_ (range iters)] (birthday-collision? person-count))
        yes (count (filter true? results))
        pct-yes (float (* 100 (/ yes iters)))]
    (format "person-count=%d yes %.5f" person-count pct-yes)))
        
(doseq [n [1 5 10 20 23 30 40 50 60 70]]
  (println (run-simulation 10000 n)))