day 9: apply optimizations to part 1
This commit is contained in:
parent
7c2b008624
commit
4e2ea7d641
53
9.rkt
53
9.rkt
|
@ -6,39 +6,38 @@
|
|||
|
||||
;; helper functions here
|
||||
|
||||
(define (part1 input)
|
||||
(define vec (list->vector input))
|
||||
(let/ec exit
|
||||
(for ([i (in-range 25 (vector-length vec))])
|
||||
(define valid?
|
||||
(for*/first ([a (in-range (- i 25) i)] [b (in-range a i)]
|
||||
#:when (= (vector-ref vec i) (+ (vector-ref vec a) (vector-ref vec b)))) #t))
|
||||
(unless valid?
|
||||
(exit (vector-ref vec i))))))
|
||||
;; linear time sum checker, assuming sorted subrange
|
||||
(define (contains-sum? vec start end wanted-sum)
|
||||
(define (helper [a start] [b (sub1 end)])
|
||||
(define cur-sum (+ (vector-ref vec a) (vector-ref vec b)))
|
||||
(cond
|
||||
[(>= a b) #f]
|
||||
[(= cur-sum wanted-sum) #t]
|
||||
[(< cur-sum wanted-sum) (helper (add1 a) b)]
|
||||
[(> cur-sum wanted-sum) (helper a (sub1 b))]))
|
||||
(vector-sort! vec < start end)
|
||||
(helper))
|
||||
|
||||
(define (part2 input)
|
||||
(define pt1 10884537)
|
||||
(define pt1-i 501)
|
||||
(let/ec exit
|
||||
(define vec (list->vector input))
|
||||
(define (cb args)
|
||||
(when (= pt1 (apply + args))
|
||||
(exit (+ (apply min args) (apply max args)))))
|
||||
(for* ([ct (in-range 3 100)] [i (in-range 0 (- pt1-i ct))])
|
||||
(define sub (vector-copy vec i (+ i ct)))
|
||||
(cb (vector->list sub)))))
|
||||
;; continuously sort the part of the vector below the iterator, and call contains-sum?
|
||||
(define (part1 vec)
|
||||
(for*/first ([i (in-range 25 (vector-length vec))] [x (in-value (vector-ref vec i))]
|
||||
#:unless (contains-sum? vec 0 i x))
|
||||
(cons i x)))
|
||||
|
||||
(module+ test
|
||||
(require rackunit)
|
||||
;; tests here
|
||||
(displayln "no tests :("))
|
||||
(define (part2 vec pt1-ans)
|
||||
(match-define (cons pt1-i pt1-val) pt1-ans)
|
||||
(for*/first ([ct (in-range 3 100)] [i (in-range 0 (- pt1-i ct))]
|
||||
[sub (in-value (vector-copy vec i (+ i ct)))]
|
||||
#:when (= pt1-val (for/fold ([x 0]) ([v (in-vector sub)]) (+ x v))))
|
||||
(+ (vector-argmin identity sub) (vector-argmax identity sub))))
|
||||
|
||||
(module+ main
|
||||
(define input (file->list "inputs/9"))
|
||||
(define input (list->vector (file->list "inputs/9")))
|
||||
;; part 1
|
||||
(answer 9 1 (part1 input))
|
||||
(define pt1 (part1 (vector-copy input)))
|
||||
(answer 9 1 (cdr pt1))
|
||||
|
||||
;; part 2
|
||||
(answer 9 2 (part2 input))
|
||||
(answer 9 2 (part2 (vector-copy input) pt1))
|
||||
|
||||
(displayln "meow"))
|
||||
|
|
Loading…
Reference in New Issue