Hackerrank Flipping bits

Challenge

Prit’s solution

(defn flipping-bits [n]
  "TOC: <1h
   Complexity: O(1), since bounded by the 32 bit limit"
  (let [bin-seq (seq (Long/toBinaryString n)) ;; looked up toBinaryString online
        size (count bin-seq)
        padded-bin-seq (concat (repeat (- 32 size) \0) bin-seq)]
    (loop [padded-bin-seq padded-bin-seq flipped-val 0]
      (if (empty? padded-bin-seq)
        flipped-val
        (recur (rest padded-bin-seq)
               (+ flipped-val
                  (if (= (first padded-bin-seq) \0)
                    (reduce * (repeat (dec (count padded-bin-seq)) 2))
                    0)))))))

(flipping-bits 4294967295)

I first convert the integer to a bit-string using Long/toBinaryString and create a sequence. Then I pad the sequence with most significant zeros to make the sequence 32 in length.

Then I loop through the sequence and add to the value, which is initialized at 0, 2^n if the sequence element is \0 and 0 otherwise, where n is the position of the bit the sequence where the least significant bit has the position 0.