2 files changed, 42 insertions(+), 2 deletions(-)

M input/day16.txt
M src/day16.lisp

@@ 1,1 1,1 @@
-()
+"59727310424796235189476878806940387435291429226818921130171187957262146115559932358924341808253400617220924411865224341744614706346865536561788244183609411225788501102400269978290670307147139438239865673058478091682748114942700860895620690690625512670966265975462089087644554004423208369517716075591723905075838513598360188150158989179151879406086757964381549720210763972463291801513250953430219653258827586382953297392567981587028568433943223260723561880121205475323894070000380258122357270847092900809245133752093782889315244091880516672127950518799757198383131025701009960944008679555864631340867924665650332161673274408001712152664733237178121872"

@@ 7,6 7,46 @@
 
 (defparameter *input* (read-day 16))
 
-(defun solve-part1 ())
+(defun to-signal (input)
+  (loop :with result := (make-array (length input))
+        :for c :across input
+        :for i :from 0
+        :do (setf (aref result i) (- (char-code c) (char-code #\0)))
+        :finally (return result)))
+
+(defun element-pattern (n)
+  (loop :with length := (* 4 (1+ n))
+        :with result := (make-array length :initial-element 100)
+        :for i :below (1+ n)
+
+        :do (setf (aref result (+ i 0)) 0
+                  (aref result (+ i (1+ n))) 1
+                  (aref result (+ i (1+ n) (1+ n))) 0
+                  (aref result (+ i (1+ n) (1+ n) (1+ n))) -1)
+        :finally (return result)))
+
+(defun next-element (phase n)
+  (loop :with element-pattern := (element-pattern n)
+        :for v :across phase
+        :for epi := 1 :then (mod (1+ epi) (length element-pattern))
+        :for ep := (aref element-pattern epi)
+        :sum (* v ep) :into result
+        :finally (return (mod (abs result) 10))))
+
+(defun next-phase (phase)
+  (loop :with result-phase := (make-array (length phase))
+        :for i :below (length phase)
+        :do (setf (aref result-phase i)
+                  (next-element phase i))
+        :finally (return result-phase)))
+
+(defun phases (phase n)
+  (loop :for current := phase :then (next-phase current)
+        :repeat n
+        :finally (return current)))
+
+(defun solve-part1 ()
+  (subseq (phases (to-signal *input*) 100)
+          0 8))
 
 (defun solve-part2 ())