master
Matthew Butterick 6 years ago
parent 2849dc3c0a
commit ecd2a403bf

@ -0,0 +1,3 @@
#1 @ 1,3: 4x4
#2 @ 3,1: 4x4
#3 @ 5,5: 2x2

@ -0,0 +1,40 @@
#lang debug br
(define fp (open-input-file "03.txt"))
(struct pt (x y) #:transparent)
(struct rect (ul lr) #:transparent)
(define (parse-claim ln)
(match-define (list left top width height)
(map string->number (cdr (regexp-match #px"(\\d+),(\\d+): (\\d+)x(\\d+)" ln))))
(rect (pt left top) (pt (+ left width) (+ top height))))
(define claims
(map parse-claim (port->lines fp)))
(define coverage (make-hash))
(for ([(claim idx) (in-indexed claims)])
(define cidx (add1 idx))
(match-define (rect (pt left top) (pt right bottom)) claim)
(for* ([x (in-range left right)]
[y (in-range top bottom)])
(hash-update! coverage (pt x y) (λ (cidxs) (cons cidx cidxs)) empty)))
(define ()
(for/sum ([cidxs (in-list (hash-values coverage))]
#:when (<= 2 (length cidxs)))
1))
(define (★★)
(define cidxss (hash-values coverage))
(for/first ([cidx (in-range 1 (add1 (length claims)))]
#:when (for/and ([cidxs (in-list cidxss)]
#:when (memv cidx cidxs))
(= (length cidxs) 1)))
cidx))
(module+ main
(require rackunit)
(check-equal? (time ()) 110827)
(check-equal? (time (★★)) 116))

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