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37 lines
968 B
Racket
37 lines
968 B
Racket
6 years ago
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#lang debug br
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(define fp (open-input-file "02.txt"))
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(define ids
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(map string-trim (port->lines fp)))
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(define ((cluster len) chars)
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(for/or ([group (in-list (group-by values chars char=?))])
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(= len (length group))))
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(define (★)
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(define charss (map string->list ids))
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(define twos (length (filter (cluster 2) charss)))
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(define threes (length (filter (cluster 3) charss)))
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(* twos threes))
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(define (differ-by-one? id id2)
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(= (length (common-chars id id2)) (sub1 (string-length id))))
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(define (common-chars id id2)
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(for/list ([c (in-string id)]
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[c2 (in-string id2)]
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#:when (char=? c c2))
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c))
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(define (★★)
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(list->string
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(for*/first ([id (in-list ids)]
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[id2 (in-list (cdr ids))]
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#:when (differ-by-one? id id2))
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(common-chars id id2))))
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(module+ main
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(require rackunit)
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(check-equal? (time (★)) 6696)
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(check-equal? (time (★★)) "bvnfawcnyoeyudzrpgslimtkj"))
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