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Day 15

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Jonathan Chan 2022-12-15 15:59:23 -05:00
parent 9462308418
commit 3d3c1f05a3
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input/15.txt Normal file
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Sensor at x=2483411, y=3902983: closest beacon is at x=2289579, y=3633785
Sensor at x=3429446, y=303715: closest beacon is at x=2876111, y=-261280
Sensor at x=666423, y=3063763: closest beacon is at x=2264411, y=2779977
Sensor at x=3021606, y=145606: closest beacon is at x=2876111, y=-261280
Sensor at x=2707326, y=2596893: closest beacon is at x=2264411, y=2779977
Sensor at x=3103704, y=1560342: closest beacon is at x=2551409, y=2000000
Sensor at x=3497040, y=3018067: closest beacon is at x=3565168, y=2949938
Sensor at x=1708530, y=855013: closest beacon is at x=2551409, y=2000000
Sensor at x=3107437, y=3263465: closest beacon is at x=3404814, y=3120160
Sensor at x=2155249, y=2476196: closest beacon is at x=2264411, y=2779977
Sensor at x=3447897, y=3070850: closest beacon is at x=3404814, y=3120160
Sensor at x=2643048, y=3390796: closest beacon is at x=2289579, y=3633785
Sensor at x=3533132, y=3679388: closest beacon is at x=3404814, y=3120160
Sensor at x=3683790, y=3017900: closest beacon is at x=3565168, y=2949938
Sensor at x=1943208, y=3830506: closest beacon is at x=2289579, y=3633785
Sensor at x=3940100, y=3979653: closest beacon is at x=2846628, y=4143786
Sensor at x=3789719, y=1225738: closest beacon is at x=4072555, y=1179859
Sensor at x=3939775, y=578381: closest beacon is at x=4072555, y=1179859
Sensor at x=3880152, y=3327397: closest beacon is at x=3404814, y=3120160
Sensor at x=3280639, y=2446475: closest beacon is at x=3565168, y=2949938
Sensor at x=2348869, y=2240374: closest beacon is at x=2551409, y=2000000
Sensor at x=3727441, y=2797456: closest beacon is at x=3565168, y=2949938
Sensor at x=3973153, y=2034945: closest beacon is at x=4072555, y=1179859
Sensor at x=38670, y=785556: closest beacon is at x=311084, y=-402911
Sensor at x=3181909, y=2862960: closest beacon is at x=3565168, y=2949938
Sensor at x=3099490, y=3946226: closest beacon is at x=2846628, y=4143786

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src/15.rkt Normal file
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#lang curly-fn racket
(require "../lib.rkt"
data/integer-set)
(define input
(for/list ([positions (problem-input 15)])
(match-define (pregexp "Sensor at x=(-?\\d+), y=(-?\\d+): closest beacon is at x=(-?\\d+), y=(-?\\d+)" sb)
positions)
(map string->number (rest sb))))
(define y 2000000)
(define bound 4000000)
(define (manhat x1 y1 x2 y2)
(+ (abs (- x1 x2)) (abs (- y1 y2))))
(define sensors
(for/list ([sb input])
(match-define `(,sx ,sy ,bx ,by) sb)
(list sx sy (manhat sx sy bx by))))
(define (impossible? x y)
(for/or ([sensor sensors])
(match-define `(,sx ,sy ,d) sensor)
(<= (manhat sx sy x y) d)))
(define part1
(for/fold ([impossibles (make-range)]
#:result (count impossibles))
([sb input])
(match-define `(,sx ,sy ,bx ,by) sb)
(define span (- (manhat sx sy bx by) (abs (- sy y))))
(if (> span 0)
(~> impossibles
(union (make-range (- sx span) (+ sx span)))
(subtract (if (= by y) (make-range bx) (make-range))))
impossibles)))
(define part2
(for/or ([sensor sensors])
(match-define `(,sx ,sy ,d) sensor)
(define d* (add1 d))
(for/or ([x (in-inclusive-range (- sx d*) (+ sx d*))]
#:when (<= 0 x bound))
(define +y (+ sy (- d* (- sx x))))
(define -y (- sy (- d* (- sx x))))
(define (freq y)
(and (<= 0 y bound)
(not (impossible? x y))
(+ (* x 4000000) y)))
(or (freq +y) (freq -y)))))
(show-solution part1 part2)