[p18] cleanup code

p18/p18.org

@@ -18,7 +18,7 @@ First parse with regex to make into a list
 	end-pos (list (- width 1) (- height 1)))
   (setq full-data data)
 #+end_src
-  now declare the usual helper functions
+  Now define the usual helper functions
 #+begin_src emacs-lisp :results none
   (defun neighbour (p dir)
     "Returns the neighbour to P in the direction DIR"
@@ -41,10 +41,19 @@ First parse with regex to make into a list
     (and (within-bounds-p p)
 	 (not (corrupted-p p))
 	 (not (visited-p p))))
+#+end_src
 
-
+Define a generic bisect function
+#+begin_src emacs-lisp :results none
+  (defun bisect (pred begin end)
+    "returns the first n between BEGIN and END such that PRED n is nil"
+    (if (eq (1+ begin) end) end
+      (let ((mid (/ (+ begin end) 2)))
+	(if (funcall pred mid) (bisect pred mid end)
+	  (bisect pred begin mid)))))
 #+end_src
 
+Now solve the problem
 #+begin_src emacs-lisp
   (defun step (new-distances)
     (let ((radius (1+ (cdar new-distances)))
@@ -53,35 +62,22 @@ First parse with regex to make into a list
 									  sphere))))))
 
   (defun out-p (n) 
-    (setq data (-take n full-data)
+    (let* ((data (-take n full-data))
-	  distances '(((0 0) . 0)))
+	  (distances '(((0 0) . 0)))
-    (setq new distances)
+	  (new distances))
 
-    (while (setq nn (step new))
+      (while (setq new (step new))
-      (setq distances (-concat nn distances)
+	(setq distances (-concat new distances)))
-	    new nn))
+      (assoc end-pos distances)))
-    (assoc end-pos distances))
-  (nth (- (bisect 'out-p 1024 (length full-data)) 1) full-data)
 
+  ;for part 1
+  (out-p 1024)
+
+  ;for part 2
+  (nth (- (bisect 'out-p 1024 (length full-data)) 1) full-data)
 #+end_src
 
 #+RESULTS:
 | 10 | 38 |
 
-#+begin_src emacs-lisp
-  (defun bisect (pred begin end)
-    (if (eq (1+ begin) end) end
-      (let ((mid (/ (+ begin end) 2)))
-	(if (funcall pred mid) (bisect pred mid end)
-	  (bisect pred begin mid))))
-    )
-
-  (defun ddd (x)
-    (< x 138))
-
-  (bisect 'ddd 10 1000)
-    #+end_src
-
-    #+RESULTS:
-    : 138