find_with_key.clj

(defn find-with-key
  ([ds key] (find-with-key (:root ds) key [:root]))
  ([ds key path]
    (if (= key (:key (:data ds)))
        path
        (if (empty? (:children ds)) nil
          (first (filter identity (for [[index child] (map-indexed list (:children ds))]
            (find-with-key ((:children ds) index) key (conj path :children index)))))))))

(def my-map {:key nil
             :root {:children [{:children []
                                :data {:key "234"}}
                               {:children [{:children []
                                            :data {:key "456"}}]
                                :data {:key "345"
                                       :x 12}}]
                    :data {:key "123"}}})

(find-with-key my-map "123")
; [:root]
(find-with-key my-map "234")
; [:root :children 0]
(find-with-key my-map "345")
; [:root :children 1]
(find-with-key my-map "456")
; [:root :children 1 :children 0]