SICP Exercise 1.11
Recursive:
(define (rf n)
(if (< n 3)
n
(+ (rf (- n 1))
(* 2 (rf (- n 2)))
(* 3 (rf (- n 3))))))
Iterative:
(define (f n)
(if (< n 3)
n
(f-iter 0 1 2 n)))
(define (f-iter a b c counter)
(if (= 0 counter)
a
(f-iter b c (+ c (* 2 b) (* 3 a)) (- counter 1))))
The iterative one took me a while to figure out. Every time I started I kept reverting back to recursive thinking.
