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day 20 part 2, yay

This commit is contained in:
efim 2022-12-25 09:40:10 +00:00
parent 974cc4993d
commit 281a0aebf4
2 changed files with 58 additions and 18 deletions
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40
day20-scratch.lisp
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@ -187,11 +187,7 @@
;; and now it works
;; god i also need to take 1000th value with overbound. ugh.
(defun get-ugh-nth (arr n)
(let* ((zero-ind (position 0 arr))
(unsafe-index (+ zero-ind n))
(safe-n (mod unsafe-index (length arr))))
(aref arr safe-n)))
(get-ugh-nth (mixing-array *test-array*) 1000)
(get-ugh-nth (mixing-array *test-array*) 2000)
@ -207,13 +203,7 @@
(get-ugh-nth (mixing-array mixed) 3000)))
;; 1797 is too low,
(defun part-1-ans (filename)
(let* ((nums (mapcar #'parse-integer (uiop:read-file-lines filename)))
(input-arr (make-array (length nums) :initial-contents nums))
(mixed (mixing-array input-arr)))
(+ (get-ugh-nth (mixing-array mixed) 1000)
(get-ugh-nth (mixing-array mixed) 2000)
(get-ugh-nth (mixing-array mixed) 3000))))
(part-1-ans "day20-test.txt")
(part-1-ans "day20-input.txt")
@ -239,3 +229,29 @@
;; what should i do about the duplicates?
;; i'd need to store elements with their initial indexes i suppose
;; and then what? iterate not over initial collection, but just over "initial" indexes
;; so, how'd i do that?
;; #'move-item works with index and move-by
;; so shouldn't depent on type of elements
;; so just #'move-elem-by-itself should take in "original index"
;; then find position in the array by the index.
;; and array would be (index value)
(zip-with-index '(2 14 1 3 5))
(input-arr "day20-test.txt")
(mixing-array (input-arr "day20-test.txt"))
;; and it works, now.
;;
;; next - extract the values from the 1000th etc
;; wait what. why did i do the mixing again. ugh
;; was that the problem, not the duplicates? will revert after getting to the answer,
;; but yikes
;; oh, i need to find 0 by value in new array
(part-1-ans "day20-test.txt")
(part-1-ans "day20-input.txt")
;; and i get a gold star.
;; let's commit and try with revert?

36
day20.lisp
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@ -92,21 +92,45 @@
))
;; we know the element value, but not it's place
(defun move-elem-by-itself (array element)
(defun move-elem-by-itself (array initial-index)
(declare (optimize (debug 3)))
(let ((i (position element array)))
(move-item array i element)))
(let ((i (position initial-index array :test (lambda (searched-index zipped)
(= searched-index (car zipped))))))
(move-item array i (second (aref array i)))))
(defun mixing-array (arr)
(let ((to-be-modified (alexandria:copy-array arr)))
(loop
for elem across arr
do (progn (move-elem-by-itself to-be-modified elem)
(format t "after moving ~a, arr: ~a~%" elem to-be-modified)
for initial-index from 0 below (length arr)
;; for elem across arr
do (progn (move-elem-by-itself to-be-modified initial-index)
;; (format t "after moving ~a, arr: ~a~%" elem to-be-modified)
))
to-be-modified))
(defun zip-with-index (ls)
(loop for v in ls
for i from 0
collect (list i v)))
(defun input-arr (filename)
(let ((nums (mapcar #'parse-integer (uiop:read-file-lines filename))))
(make-array (length nums) :initial-contents (zip-with-index nums))))
(defun get-ugh-nth (arr n)
;; need to find 0 by value in the (index, value) array
(let* ((zero-ind (position 0 arr :test (lambda (searched-value zipped)
(= searched-value (second zipped)))))
(unsafe-index (+ zero-ind n))
(safe-n (mod unsafe-index (length arr))))
(second (aref arr safe-n))))
(defun part-1-ans (filename)
(let* ((input-arr (input-arr filename))
(mixed (mixing-array input-arr)))
(format t "getting part 1, mixed array: ~a~%" mixed)
(+ (get-ugh-nth mixed 1000)
(get-ugh-nth mixed 2000)
(get-ugh-nth mixed 3000))))
(5am:run! 'day20-tests)