salesman

salesman.clj

(defn move-to-front [first others]
  "Moves an item to the front of the list"
  (cons first (remove #(identical? first %) others)))
(defn first-level [list]
  "Returns a list of all first-level permutations."
  (map #(move-to-front % list) list))
(defn permute-deeper [depth list]
  "Takes a list and a depth. Ignores the first few items according to the depth, and returns a list of all permutations for the rest."
  (let [head-of-list (take depth list)
        rest-of-list (drop depth list)
        add-head    #(reduce conj % (reverse head-of-list))]
    (map #(add-head (move-to-front % rest-of-list)) rest-of-list)))

;; (first-level [1 2 3])
;; ((1 2 3) (2 1 3) (3 1 2))
;; (map #(permute-deeper 1 %) (first-level [1 2 3]))
;; (((1 2 3) (1 3 2)) ((2 1 3) (2 3 1)) ((3 1 2) (3 2 1)))

;; goal:
;; (permute [1 2 3])
;; ((1 2 3) (1 3 2) (2 1 3) (2 3 1) (3 1 2) (3 2 1))