[p1] Slightly better

p1/p1.org

@@ -24,32 +24,30 @@ number of 0's mod 100; that is what we need for part 1
 : 962
 
 For part 2, This ain't pretty, but it works:
+- we count the number of full turns that have been done in each
+  rotation
+- we add the number of times we landed at 0 by turning left and then
+  right immediately after; these have not been counted above
 #+begin_src emacs-lisp
   (defun advent/consecutive-pairs (list)
     (-zip-pair list (cdr list)))
 
-  (+
-   (-sum (--map (abs (- (car it) (cdr it)))
-                (advent/consecutive-pairs
-                 (--map (floor it 100) (-running-sum (append '(50) data))))))
-
-   (length
-    (--filter (and (eq (car it) 0) (< (cdr it) 0))
-              (-zip-pair
-               (cdr (--map (mod it 100) (-running-sum (append '(50) data))))
-               data)))
-
-  (* -1 (length
-    (--filter (and (eq (car it) 0) (< (cdr it) 0))
-              (-zip-pair
-               (cdr (--map (mod it 100) (-running-sum (append '(50) data))))
-               (cdr data))))))
+  (let ((number-list (-running-sum (append '(50) data))))
+    (+
+     (-sum (--map (abs (- (car it) (cdr it)))
+                  (advent/consecutive-pairs
+                   (--map (floor it 100) number-list))))
+
+     (length
+      (--filter (and (eq (car it) 0) (< (cdr it) 0))
+                (-zip-pair
+                 (cdr (--map (mod it 100) number-list)) data)))
+
+     (* -1 (length
+            (--filter (and (eq (car it) 0) (< (cdr it) 0))
+                      (-zip-pair
+                       (cdr (--map (mod it 100) number-list)) (cdr data)))))))
 #+end_src
 
 #+RESULTS:
 : 5782
-
-#+begin_src emacs-lisp
-  (floor -5 100)
-#+end_src
-*