>>123,124
Nice. I also just realized that now I have no reason to save the R values. Their queue has been removed.
(use-modules (ice-9 q))
(define (sequence n)
(let* ((rs 7) ; Smallest R value unused.
(ss (make-q)) ; Queue of S values.
(r 7) ; Current R value.
(s 5) ; Current S value.
(negsum -7) ; Negative sum of unused R values.
(pos 3) ; Smallest n in the queues.
(n (- n 1))) ; Off by one.
(enq! ss s)
(let loop ((i 4))
(when (<= (+ s r) (+ i n))
(set! r (+ r s))
(set! s (+ s 1))
(set! negsum (- negsum r))
(when (= s rs)
(set! rs (+ rs (q-front ss)))
(set! negsum (+ negsum s))
(set! s (+ s 1))
(set! pos (+ pos 1))
(deq! ss))
(enq! ss s)
(loop (+ i 1))))
(list pos negsum r (cadr ss))))
(define (sum m n)
(* (/ (- m n -1) 2) (+ m n)))
(define (jump n)
(cond
((= n 1) 1)
((= n 2) 3)
((= n 3) 7)
((= n 4) 12)
(else
(let* ((seq (sequence n))
(m (list-ref seq 0))
(ns (list-ref seq 1))
(r' (list-ref seq 2))
(s' (list-ref seq 3))
(n' (+ m -1))
(s (+ s' (- n n'))))
(+ r' (sum (- s 1) s') ns)))))This is my last update for today as it feels spammy. If you are going to rerun the benchmarks, please use this version.