(define (fizzbuzz til)
  (let loop ([n 1]
             [fizz 2]
             [buzz 4])
    (when (<= n til)
      (cond [(and (zero? fizz) (zero? buzz))
             (displayln 'fizzbuzz)
             (loop (+ n 1) 2 4)]
            [(zero? fizz)
             (displayln 'fizz)
             (loop (+ n 1) 2 (- buzz 1))]
            [(zero? buzz)
             (displayln 'buzz)
             (loop (+ n 1) (- fizz 1) 4)]
            [else (displayln n)
                  (loop (+ n 1) (- fizz 1) (- buzz 1))]))))

;; C2W1
(define max-size 100)

(define memo (make-vector (+ max-size 1) #f))
(vector-set! memo 0 0)
(vector-set! memo 1 1)

(define (fibs n)
  (if (<= n max-size)
      (or (vector-ref memo n)
          (let ([res (+ (fibs (- n 1)) (fibs (- n 2)))])
            (vector-set! memo n res)
            res))
      (+ (fibs (- n 1)) (fibs (- n 2)))))