commit - 58c83f8af7c4abc47f02dc051fd17da85272eb0d
commit + 18c13061da0c7b642446e64b7dc1a561c3958fc0
blob - 5b020d98d87433bfd0ea27bbafb88ab2fa205c1d
blob + f4b0f56ab9800d5825e2ce332f188bf935387e99
--- src/day-7.lisp
+++ src/day-7.lisp
(defparameter *operators-task-1* '(+ *))
(defparameter *operators-task-2* '(+ * combine))
-(defun map-operation-combinations (function length operators)
- (apply #'map-product function (loop for n from 1 below length
- collect operators)))
+(defun map-operator-combinations (function length operators)
+ (labels ((%map (current n)
+ (if (= n length)
+ (funcall function current)
+ (loop with nn = (1+ n)
+ for operator in operators
+ do (%map (cons operator current) nn)))))
+ (%map nil 0)))
(defun number-digits (number)
(if (zerop number)
(defun combine (num-1 num-2)
(+ (* num-1 (expt 10 (number-digits num-2))) num-2))
-(defun calculate (operators numbers)
+(defun calculate (operators numbers test-value)
(loop with current = (car numbers)
for operator in operators
for next in (cdr numbers)
do (setf current (funcall operator current next))
+ when (> current test-value)
+ do (return current)
finally (return current)))
(defun test-value-valid-p (test-value numbers operators)
- (map-operation-combinations (lambda (&rest operators)
- (when (= test-value (calculate operators numbers))
- (return-from test-value-valid-p t)))
- (length numbers)
- operators)
+ (map-operator-combinations (lambda (operators)
+ (when (= test-value (calculate operators numbers test-value))
+ (return-from test-value-valid-p t)))
+ (1- (length numbers))
+ operators)
nil)
(defun day-7 (input)
