September Morn Update

2019-09-12 10:33:56 -07:00 · 2019-09-12 10:33:56 -07:00 · aac6731f2c
commit aac6731f2c
parent 4e2d22a71d
6856 changed files with 141342 additions and 21127 deletions
--- a/Task/Fibonacci-sequence/Clojure/fibonacci-sequence-7.clj
+++ b/Task/Fibonacci-sequence/Clojure/fibonacci-sequence-7.clj
@ -1,6 +1,11 @@
 (defn fib [n]
-  (case n
-    0 0
-    1 1
-    (+ (fib (- n 1))
-       (fib (- n 2)))))
+  (letfn [(fib* [n]
+            (if (zero? n)
+              [0 1]
+              (let [[a b] (fib* (quot n 2))
+                    c (*' a (-' (*' 2 b) a))
+                    d (+' (*' b b) (*' a a))]
+                (if (even? n)
+                  [c d]
+                  [d (+' c d)]))))]
+    (first (fib* n))))