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- #lang racket
- (require "../lib/utils.rkt")
- (define lines
- (call-with-input-file "input"
- (λ (fp) (get-lines fp))))
- (set! lines (list->vector lines))
- (define (expand-rows lines)
- (let loop ((cur (vector->list lines)) (ret '()))
- (if (null? cur)
- (list->vector (reverse ret))
- (if (andmap (λ (c) (char=? c #\.)) (string->list (car cur)))
- (loop (cdr cur) (cons (car cur) (cons (car cur) ret)))
- (loop (cdr cur) (cons (car cur) ret))))))
- (define (transpose linesvec)
- (define lines (vector->list linesvec))
- (define width (string-length (vector-ref linesvec 0)))
- (define new-lines (make-vector width))
- (let loop ((i 0))
- (if (>= i width)
- new-lines
- (let ()
- (define char-list (map (λ (l) (string-ref l i)) lines))
- (vector-set! new-lines i (list->string char-list))
- (loop (+ i 1))))))
- (define universe
- (transpose (expand-rows (transpose (expand-rows lines)))))
- (define height (vector-length universe))
- (define width (string-length (vector-ref universe 0)))
- (define (get-galaxies universe)
- (define (char-at x y) (string-ref (vector-ref universe y) x))
- (let loop ((x 0) (y 0) (ret '()))
- (if (>= y height)
- (list->vector (reverse ret))
- (if (>= x width)
- (loop 0 (+ y 1) ret)
- (if (char=? #\# (char-at x y))
- (loop (+ x 1) y (cons (cons x y) ret))
- (loop (+ x 1) y ret))))))
- (define galaxies (get-galaxies universe))
- (define (gen-pairs n)
- (let loop ((i 0) (j 1) (ret '()))
- (if (>= i n)
- (reverse ret)
- (if (>= j n)
- (loop (+ 1 i) (+ 2 i) ret)
- (loop i (+ 1 j) (cons (cons i j) ret))))))
- (define (distance n1 n2)
- (define x1 (car (vector-ref galaxies n1)))
- (define x2 (car (vector-ref galaxies n2)))
- (define y1 (cdr (vector-ref galaxies n1)))
- (define y2 (cdr (vector-ref galaxies n2)))
- (+ (abs (- x1 x2)) (abs (- y1 y2))))
- (apply
- +
- (map (λ (x) (distance (car x) (cdr x)))
- (gen-pairs (vector-length galaxies))))
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