|
|
#lang br
|
|
|
(require racket/file rackunit)
|
|
|
|
|
|
(define (string->ints str) (map string->number (string-split str #px",\\s*")))
|
|
|
(define (string->regs str) (list->vector (string->ints str)))
|
|
|
|
|
|
(define ((binarize proc) x y) (if (proc x y) 1 0))
|
|
|
|
|
|
(define (make-runner program [calling-thd (current-thread)])
|
|
|
(thread (λ ()
|
|
|
(define regs (string->regs program))
|
|
|
(define (maybe-enlarge-regs ptr)
|
|
|
(unless (< ptr (vector-length regs))
|
|
|
(define newvec (make-vector (add1 ptr) 0))
|
|
|
(vector-copy! newvec 0 regs)
|
|
|
(set! regs newvec))
|
|
|
regs)
|
|
|
(define (reg-ref ptr) (vector-ref (maybe-enlarge-regs ptr) ptr))
|
|
|
(define (reg-set! ptr val) (vector-set! (maybe-enlarge-regs ptr) ptr val))
|
|
|
(define relative-base 0)
|
|
|
(let/ec terminate
|
|
|
(let loop ([ptr 0])
|
|
|
(define inst (for/list ([c (in-string (~r (reg-ref ptr) #:min-width 5 #:pad-string "0"))])
|
|
|
(string->number (string c))))
|
|
|
(define-values (opcode resolve)
|
|
|
(match inst
|
|
|
[(list d4 d3 d2 d1 d0)
|
|
|
(values (+ (* 10 d1) d0)
|
|
|
(λ (ptr offset)
|
|
|
(define parameter-value (match offset [1 d2] [2 d3] [3 d4]))
|
|
|
(define ptr-resolver (match parameter-value
|
|
|
[0 reg-ref] ; position
|
|
|
[1 values] ; immediate
|
|
|
[2 (compose1 (λ (ptr) (+ relative-base ptr)) reg-ref)])); relative
|
|
|
(ptr-resolver (+ ptr offset))))]))
|
|
|
(define next-ptr
|
|
|
(match opcode
|
|
|
[(or 1 2 7 8) ; 4-arity: add & multiply & compare
|
|
|
(reg-set! (resolve ptr 3) ((match opcode
|
|
|
[1 +]
|
|
|
[2 *]
|
|
|
[7 (binarize <)]
|
|
|
[8 (binarize =)]) (reg-ref (resolve ptr 1)) (reg-ref (resolve ptr 2))))
|
|
|
(+ ptr 4)]
|
|
|
[(or 3 4 9) ; 2-arity: input & output
|
|
|
(match opcode
|
|
|
[3 (reg-set! (resolve ptr 1) (thread-receive))]
|
|
|
[4 (thread-send calling-thd (reg-ref (resolve ptr 1)))]
|
|
|
[9 (set! relative-base (+ relative-base (reg-ref (resolve ptr 1))))])
|
|
|
(+ ptr 2)]
|
|
|
[(or 5 6) ; 3-arity: jump
|
|
|
(if ((match opcode
|
|
|
[5 not]
|
|
|
[6 values]) (zero? (reg-ref (resolve ptr 1))))
|
|
|
(reg-ref (resolve ptr 2))
|
|
|
(+ ptr 3))]
|
|
|
[99 (thread-send calling-thd 'done) (terminate)]
|
|
|
[_ (error "unknown opcode" opcode)]))
|
|
|
(loop next-ptr))))))
|
|
|
|
|
|
(define th (make-runner (file->string "15.rktd")))
|
|
|
|
|
|
(define (step where)
|
|
|
(thread-send th where)
|
|
|
(match (thread-receive)
|
|
|
[0 'wall]
|
|
|
[1 'empty]
|
|
|
[2 'oxygen]))
|
|
|
|
|
|
(define (dir->cmd dir)
|
|
|
(match dir
|
|
|
[+i 1]
|
|
|
[-i 2]
|
|
|
[-1 3]
|
|
|
[1 4]))
|
|
|
|
|
|
(require graph)
|
|
|
(define g (unweighted-graph/undirected null))
|
|
|
|
|
|
(define (turn-left dir) (* dir +i))
|
|
|
(define (turn-right dir) (/ dir +i))
|
|
|
|
|
|
(define (explore loc [dir +i])
|
|
|
(define left-dir (turn-left dir))
|
|
|
(match (step (dir->cmd left-dir))
|
|
|
['wall (explore loc (turn-right dir))]
|
|
|
[res (add-edge! g loc (+ loc left-dir))
|
|
|
(match res
|
|
|
['empty (explore (+ loc left-dir) left-dir)]
|
|
|
['oxygen (+ loc left-dir)])]))
|
|
|
|
|
|
(define oxygen-loc (explore 0))
|
|
|
(fewest-vertices-path g 0 oxygen-loc)
|