bucketize.clj

(def m {:a 1 :b 2 :c 3 :d 4 :e 5 :f 6 :g 7 :h 8 :i 9 :j 534})

;; Split to chunks by count
(defn bucketize [rows]
  (reduce 
   (fn [acc [k v]]
     (if (< (count (last acc)) 3)
       (assoc-in acc [(- (count acc) 1)] (conj (last acc) v))
       (conj acc [v])))
   [[]] rows))

(bucketize m)
;; [[5 7 3] [534 8 2] [4 6 9] [1]]

;; Split to chunks by sum
(defn bucketize [rows]
  (reduce 
   (fn [acc [k v]]
     (if (< (reduce (fn [a x] (+ a x v)) 0 (last acc)) 9)
       (assoc-in acc [(- (count acc) 1)] (conj (last acc) v))
       (conj acc [v])))
   [[]] rows))

(bucketize m)
;; [[5] [7] [3] [534] [8] [2 4] [6] [9] [1]]