rotate 45

naname.clj

(defn rotate-90 [arr]
  (reverse (apply map vector arr)))

(defn rotate [arr n]
  (reduce (fn [x _] (rotate-90 x)) arr (range n)))

(defn slide [arr]
  (let [width (dec (count (first arr)))]
    (for [[i row] (seq-utils/indexed arr)]
      (concat (repeat i ::empty) row (repeat (- width i) ::empty)))))

(defn rearrange [arr angle]
  (let [arr (rotate arr 3) ;; initial position
        r-num (quot angle 2)
        arr (rotate arr r-num)
        tilt? (= (rem angle 2) 1)
        arr (if tilt? (slide arr) arr)
        height (count arr)
        width (count (first arr))]
    (for [x (reverse (range width))]
      (filter #(not= ::empty %)
              (map (fn [y] (nth (nth arr y) x)) (range height))))))


(rearrange a 0)
=> ((1 2 3 4) (11 12 13 14) (21 22 23 24) (31 32 33 34))

(rearrange a 1)
=> ((4) (3 14) (2 13 24) (1 12 23 34) (11 22 33) (21 32) (31))

(rearrange a 2)
=> ((4 14 24 34) (3 13 23 33) (2 12 22 32) (1 11 21 31))

(rearrange a 3)
=> ((34) (24 33) (14 23 32) (4 13 22 31) (3 12 21) (2 11) (1))