Ain't pretty, but it works

p1/p1.org

@@ -0,0 +1,55 @@
+#+title: Solution to p1
+
+First load the data as a list of positive or negative numbers
+#+begin_src emacs-lisp :results none
+  (with-temp-buffer
+      (insert-file-contents "input")
+      (advent/replace-multiple-regex-buffer
+       '(("L" . "-")
+         ("R" . "")))
+      (goto-char (point-min))
+      (insert "(setq data '(")
+      (goto-char (point-max))
+      (insert "))")
+      (eval-buffer))
+#+end_src
+
+Then add the rotations starting from the initial offset and count the
+number of 0's mod 100; that is what we need for part 1
+#+begin_src emacs-lisp
+  (length (--filter (= 0 it) (--map (mod it 100) (-running-sum (append '(50) data)))))
+#+end_src
+
+#+RESULTS:
+: 962
+
+For part 2, This ain't pretty, but it works:
+#+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))))))
+#+end_src
+
+#+RESULTS:
+: 5782
+
+#+begin_src emacs-lisp
+  (floor -5 100)
+#+end_src
+*