;; mine

(defn factorial [n]
  (loop [i 1
         result 1]
  (if (= i n)
    (* result i)
    (recur (inc i) (* result i)))))

;; solution

(defn factorial [n]
  (loop [n n
         result 1]
  (if (= 0 n)
    result
    (recur (dec n) (* result n)))))