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29 lines
873 B
Racket
29 lines
873 B
Racket
7 years ago
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#lang reader "../aoc-lang.rkt"
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(require graph)
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(provide (rename-out [#%mb #%module-begin]))
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(define-macro (#%mb (STARS) (NUM <-> . NUMS) ...)
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#'(#%module-begin
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(define g (unweighted-graph/undirected null))
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(for-each (curry add-edge! g NUM) (list . NUMS)) ...
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(if (eq? 'STARS '★)
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(programs-in-group g 0)
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(number-of-groups g (list NUM ...)))))
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(define (programs-in-group g x) (length (group-of g x)))
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(define (group-of g x)
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(define-values (connects _) (dijkstra g x))
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(for/list ([(k v) (in-hash connects)]
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#:when (integer? v))
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k))
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(define (number-of-groups g nums)
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(for/fold ([nums-seen null]
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[group-count 0]
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#:result group-count)
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([num (in-list nums)]
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#:unless (memv num nums-seen))
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(values (append (group-of g num) nums-seen) (add1 group-count))))
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