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day 10 part 2 in common lisp

master
cow 2022-12-28 23:28:57 -05:00
parent f1134f4b00
commit 8b48928e9e
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common-lisp/day-10/solution.lisp
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@ -25,15 +25,26 @@
(in-package :advent-of-code-day-10)
(defun signal-strength-at-cycle (instructions cycle)
(defun register-value-at-cycle (instructions cycle)
(iter (for instruction in instructions)
(for noop? = (not (consp instruction)))
(for counter initially 1 then (+ counter (if noop? 1 2)))
(for register initially 1 then (if noop? register (+ register (cdr instruction))))
(for previous-counter previous counter)
(for previous-register previous register)
(for register initially 1 then (if noop? register (+ register (cdr instruction))))
(for previous-register-value previous register)
(when (> counter cycle)
(return (* cycle previous-register)))))
(return (if (first-iteration-p)
1
previous-register-value)))
(finally (return register))))
(defun signal-strength-at-cycle (instructions cycle)
(* (register-value-at-cycle instructions cycle) cycle))
(defun sprite-intersects? (pixel sprite)
(let ((sprite-start (- sprite 1))
(sprite-end (+ sprite 1)))
(and (>= pixel sprite-start)
(<= pixel sprite-end))))
(defun parse-input (lines)
(iter (for line in lines)
@ -41,6 +52,25 @@
:noop
(cons :addx (parse-integer (cadr (str:split " " line))))))))
(defun solution-part-2 (instructions)
(iter (with screen = (make-array '(6 40) :element-type 'character :initial-element #\.))
(for cycle from 1 to 240)
(for register = (register-value-at-cycle instructions cycle))
(for x = (mod (- cycle 1) 40))
(for (values y nil) = (floor (- cycle 1) 40))
(when (sprite-intersects? x register)
(setf (aref screen y x) #\#))
(finally (return screen))))
(defun print-screen (screen stream)
(iter (for y from 0 to 5)
(iter (for x from 0 to 39)
(format stream "~a" (aref screen y x)))
(format stream "~%")))
;; test cases
(let ((input (parse-input (read-file-lines "example.txt"))))
(assert (= 420 (signal-strength-at-cycle input 20)))
(assert (= 1140 (signal-strength-at-cycle input 60)))
@ -55,6 +85,20 @@
(assert (= 14320 (iter (for cycle from 20 to 240 by 40)
(sum (signal-strength-at-cycle input cycle))))))
;; this puzzle relies on visual confirmation to determine whether its correct or not
;; so we just print the result to the terminal
(let* ((input (parse-input (read-file-lines "example.txt")))
(screen (solution-part-2 input)))
(format t "~&~%screen for example input~%~%")
(print-screen screen t))
(let* ((input (parse-input (read-file-lines "input.txt")))
(screen (solution-part-2 input)))
(format t "~&~%screen for normal input~%~%")
(print-screen screen t))
;; Local Variables:
;; mode: lisp
;; End: