14 lines
590 B
Racket
14 lines
590 B
Racket
#lang racket
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(define seen (make-hash))
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(define semordnilaps '())
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(call-with-input-file "/usr/share/dict/words"
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(λ(i) (for ([l (in-lines i)])
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(define r (list->string (reverse (string->list l))))
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(unless (equal? r l)
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(hash-set! seen l #t)
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(when (hash-ref seen r #f)
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(set! semordnilaps (cons (list r l) semordnilaps)))))))
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(printf "Total semordnilaps found: ~s\n" (length semordnilaps))
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(printf "The five longest ones:\n")
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(for ([s (take (sort semordnilaps > #:key (compose1 string-length car)) 5)])
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(apply printf " ~s ~s\n" s))
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