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-rw-r--r--AoC2023/day09/solver.lisp62
1 files changed, 30 insertions, 32 deletions
diff --git a/AoC2023/day09/solver.lisp b/AoC2023/day09/solver.lisp
index d515317..3df0cc3 100644
--- a/AoC2023/day09/solver.lisp
+++ b/AoC2023/day09/solver.lisp
@@ -1,46 +1,44 @@
;;03:39
+;;04:07 Solved
+;;05:24 Painful refactorins
(ql:quickload '(fiveam arrows transducers))
+
(defparameter eg-input "0 3 6 9 12 15
1 3 6 10 15 21
10 13 16 21 30 45")
(defun row-reducer (row)
- (loop for (a b) on row by #'cdr
- until (null b)
- collect (- b a)))
+ (mapcar #'- (cdr row) row))
(defun terminal-p (row)
- (every #'zerop row))
+ (every #'= (cdr row) row))
-(defun forward (row)
+(defun get-coefs (row pick &optional acc)
(if (terminal-p row)
- 0
- (+ (forward (row-reducer row)) (car (last row)))))
+ (nreverse (cons (funcall pick row) acc))
+ (get-coefs (row-reducer row) pick (cons (funcall pick row) acc))))
-(defun backward (row)
- (if (terminal-p row)
- 0
- (- (car row) (backward (row-reducer row)))))
-
-(defun solver1 (lines)
- (arrows:->>
- lines
- (mapcar (lambda (line)
- (forward
- (mapcar #'parse-integer (uiop:split-string line)))))
- (apply #'+)))
-
-(defun solver2 (lines)
- (arrows:->>
- lines
- (mapcar (lambda (line)
- (backward
- (mapcar #'parse-integer (uiop:split-string line)))))
- (apply #'+)))
+(defun parse-line (line)
+ (mapcar #'parse-integer (uiop:split-string line)))
-(fiveam:test solutions
- (fiveam:is (= 114 (solver1 (uiop:split-string eg-input :separator '(#\Newline)))))
- (fiveam:is (= 2105961943 (solver1 (uiop:read-file-lines "input"))))
+(defun forward (line)
+ (reduce #'+ (get-coefs line (lambda (a) (car (last a))))))
- (fiveam:is (= 2 (solver2 (uiop:split-string eg-input :separator '(#\Newline)))))
- (fiveam:is (= 1019 (solver2 (uiop:read-file-lines "input")))))
+(defun backward (line)
+ (reduce #'- (get-coefs line #'car) :from-end t))
+
+(defun solver (lines key)
+ (reduce #'+
+ (mapcar #'parse-line lines)
+ :key key))
+
+(fiveam:test solutions
+ (fiveam:is (= 114 (solver (uiop:split-string eg-input :separator '(#\Newline))
+ #'forward)))
+ (fiveam:is (= 2105961943 (solver (uiop:read-file-lines "input")
+ #'forward)))
+
+ (fiveam:is (= 2 (solver (uiop:split-string eg-input :separator '(#\Newline))
+ #'backward)))
+ (fiveam:is (= 1019 (solver (uiop:read-file-lines "input")
+ #'backward))))