25 lines
632 B
Common Lisp
25 lines
632 B
Common Lisp
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(asdf:load-system "cl-strings")
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(require :cl-strings)
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(defvar *input*
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(mapcar (lambda (line)
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(mapcar (lambda (column) (parse-integer column))
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(cl-strings:split line " ")))
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(uiop:with-safe-io-syntax ()
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(uiop:read-file-lines "input.txt"))))
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(defun gradual-diff-p (record)
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(cond
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((null (cdr record)) t)
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((not (< 0 (abs (- (car record) (cadr record))) 4)) nil)
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(t (gradual-diff-p (cdr record)))))
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(defun safep (record)
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(and (or (apply #'< record)
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(apply #'> record))
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(gradual-diff-p record)))
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(length (delete nil (mapcar #'safep *input*)))
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