67 lines
2.4 KiB
Common Lisp
67 lines
2.4 KiB
Common Lisp
(declaim (optimize (speed 3) (safety 0) (debug 0)))
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(defconstant +loop-count+ 1000000)
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(defconstant +expected-checksum+ 3500013)
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(defstruct (packet (:constructor %make-packet (digits))) digits)
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(defstruct (packet-state (:constructor %make-packet-state (tag payload))) tag payload)
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(declaim (ftype (function () fixnum) configured-loop-count))
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(defun configured-loop-count ()
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(handler-case
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(let ((line (read-line *standard-input* nil nil)))
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(if line
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(let ((value (parse-integer line :junk-allowed t)))
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(if (> value 0) value +loop-count+))
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+loop-count+))
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(error () +loop-count+)))
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(declaim (ftype (function () packet-state) live-state))
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(defun live-state ()
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(%make-packet-state :live (%make-packet #(2 7 1 8 2 8 1 8))))
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(declaim (ftype (function () packet-state) cached-state))
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(defun cached-state ()
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(%make-packet-state :cached (%make-packet #(1 6 1 8 0 3 4 5))))
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(declaim (ftype (function (fixnum packet-state packet-state) packet-state) select-state))
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(defun select-state (i live cached)
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(declare (type fixnum i))
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(if (zerop (rem i 2))
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live
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cached))
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(declaim (ftype (function (packet-state fixnum) fixnum) state-digit))
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(defun state-digit (state index)
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(declare (type packet-state state)
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(type fixnum index))
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(let* ((payload (packet-state-payload state))
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(digits (packet-digits payload))
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(value (svref digits index)))
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(declare (type simple-vector digits)
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(type fixnum value))
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(case (packet-state-tag state)
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(:missing 0)
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(otherwise value))))
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(declaim (ftype (function (fixnum) fixnum) enum-struct-payload-loop))
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(defun enum-struct-payload-loop (limit)
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(declare (type fixnum limit))
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(loop with i of-type fixnum = 0
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with acc of-type fixnum = 13
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with live of-type packet-state = (live-state)
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with cached of-type packet-state = (cached-state)
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while (< i limit)
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do (let* ((next (+ acc (state-digit (select-state i live cached) (rem i 8))))
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(bounded (if (> next 1000000000)
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(- next 1000000000)
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next)))
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(declare (type fixnum next bounded))
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(setf acc bounded
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i (+ i 1)))
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finally (return acc)))
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(let ((result (enum-struct-payload-loop (configured-loop-count))))
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(format t "~D~%" result)
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(sb-ext:exit :code (if (= result +expected-checksum+) 0 1)))
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