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day 22: some cleanup/optimization

This commit is contained in:
xenia 2020-12-22 01:54:39 -05:00
parent b4d5abe1f2
commit 9ef0e2eec1
2 changed files with 40 additions and 50 deletions
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62
22.rkt
View File

@ -3,63 +3,51 @@
(require "scripts/aoc.rkt")
;; solution for day 22
(define (score cards)
(define (score cards)
(for/sum ([card (in-list cards)] [mult (in-range (length cards) 0 -1)])
(* card mult)))
(define (play p1 p2)
(cond
[(empty? p1) (score p2)]
[(empty? p2) (score p1)]
[else
(define p1-card (first p1))
(define p2-card (first p2))
(cond
[(> p1-card p2-card) (play (append (rest p1) (list p1-card p2-card)) (rest p2))]
[else (play (rest p1) (append (rest p2) (list p2-card p1-card)))])]))
(define (play p1 p2)
(match* (p1 p2)
[('() _) (score p2)]
[(_ '()) (score p1)]
[((cons p1-card p1-rest) (cons p2-card p2-rest))
(if (> p1-card p2-card)
(play (append p1-rest (list p1-card p2-card)) p2-rest)
(play p1-rest (append p2-rest (list p2-card p1-card))))]))
(define (part1 input)
(match-define (list p1 p2) input)
(play p1 p2))
(define (part2 input)
(match-define (list p1 p2) input)
(define memo (make-hash))
(define (do-memo level p1 p2)
(hash-update! memo level (lambda (x) (set-add x (list p1 p2))) (set)))
(define (play/recur p1 p2 [level 0])
; (printf "~a ~a\n" p1 p2)
(define/memoized (play/recur p1 p2)
(define local-memo (mutable-set))
(let loop ([p1 p1] [p2 p2])
(cond
[(set-member? (hash-ref memo level (set)) (list p1 p2)) (cons 'p1 (score p1))]
[(empty? p1) (cons 'p2 (score p2))]
[(empty? p2) (cons 'p1 (score p1))]
[(set-member? local-memo (list p1 p2)) (cons 'p1 p1)]
[(empty? p1) (cons 'p2 p2)]
[(empty? p2) (cons 'p1 p1)]
[else
(define p1-card (first p1))
(define p1-rest (rest p1))
(define p2-card (first p2))
(define p2-rest (rest p2))
(set-add! local-memo (list p1 p2))
(match-define (cons p1-card p1-rest) p1)
(match-define (cons p2-card p2-rest) p2)
(cond
[(and (>= (length p1-rest) p1-card)
(>= (length p2-rest) p2-card))
(match-define (cons winner score)
(play/recur (take p1-rest p1-card) (take p2-rest p2-card) (add1 level)))
; (printf "submatch ~a\n" winner)
(do-memo level p1 p2)
(play/recur (take p1-rest p1-card) (take p2-rest p2-card)))
(if (symbol=? winner 'p1)
(play/recur (append p1-rest (list p1-card p2-card)) p2-rest level)
(play/recur p1-rest (append p2-rest (list p2-card p1-card)) level))]
(loop (append p1-rest (list p1-card p2-card)) p2-rest)
(loop p1-rest (append p2-rest (list p2-card p1-card))))]
[(> p1-card p2-card)
(do-memo level p1 p2)
(play/recur (append p1-rest (list p1-card p2-card)) p2-rest level)]
(loop (append p1-rest (list p1-card p2-card)) p2-rest)]
[else
(do-memo level p1 p2)
(play/recur p1-rest (append p2-rest (list p2-card p1-card)) level)])]))
(loop p1-rest (append p2-rest (list p2-card p1-card)))])])))
(cdr (play/recur p1 p2)))
(score (cdr (play/recur p1 p2))))
;; parse input file
(define (parse fname)
@ -68,6 +56,8 @@
(map string->number (rest (string-split p1 "\n")))
(map string->number (rest (string-split p2 "\n")))))
(time (part2 (parse "/tmp/adventofcode-2020/input/22.txt")))
(module+ test
(require rackunit)
;; tests here

8
scripts/aoc.rkt
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@ -26,11 +26,11 @@
;; makes a memoization wrapper around a function
(define (memoize func)
(define memo (make-hash))
(lambda (arg)
(hash-ref! memo arg (λ () (func arg)))))
(lambda args
(hash-ref! memo args (λ () (apply func args)))))
(define-simple-macro (define/memoized (name:id arg:id) body:expr ...+)
(define name (memoize (λ (arg) body ...))))
(define-simple-macro (define/memoized (name:id arg:id ...) body:expr ...+)
(define name (memoize (λ (arg ...) body ...))))
;; helper for maximum-bipartite-matching
;; given an edge list where each first item corresponds to the left set and each second item