metaljoe_codekata / kata2 / code_kata_2b.clj

; http://codekata.pragprog.com/2007/01/kata_two_karate.html


(defn
  #^{:test (fn []
			 (assert (= -1 (chop 3 []) ))
			 (assert (= -1 (chop 3 [1]) ))
			 (assert (=  0 (chop 1 [1]) ))

			 (assert (=  0 (chop 1 [1 3 5]) ))
			 (assert (=  1 (chop 3 [1 3 5]) ))
			 (assert (=  2 (chop 5 [1 3 5]) ))
			 (assert (= -1 (chop 0 [1 3 5]) ))
			 (assert (= -1 (chop 2 [1 3 5]) ))
			 (assert (= -1 (chop 4 [1 3 5]) ))
			 (assert (= -1 (chop 6 [1 3 5]) ))

			 (assert (=  0 (chop 1 [1 3 5 7]) ))
			 (assert (=  1 (chop 3 [1 3 5 7]) ))
			 (assert (=  2 (chop 5 [1 3 5 7]) ))
			 (assert (=  3 (chop 7 [1 3 5 7]) ))
			 (assert (= -1 (chop 0 [1 3 5 7]) ))
			 (assert (= -1 (chop 2 [1 3 5 7]) ))
			 (assert (= -1 (chop 4 [1 3 5 7]) ))
			 (assert (= -1 (chop 6 [1 3 5 7]) ))
			 (assert (= -1 (chop 8 [1 3 5 7]) )) ) }
  chop
  [item list]
  (if (empty? list)
	-1
	(loop [ min 0 mid (quot (count list) 2) max (count list)]
	  (if (= item (get list mid))
		mid
		(if (or (= mid min) (= mid max))
		  -1
		  (if (< item (get list mid))
			(recur min (quot (+ mid min) 2) mid)       ; look left
			(recur mid (quot (+ mid max) 2) max))))))) ; look right

(test #'chop)
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