breadth-first

p16/p16.org

@@ -4,7 +4,7 @@ Load map
 #+begin_src emacs-lisp :results none
   (require 'dash)
   (with-temp-buffer
-      (insert-file-contents "input")
+      (insert-file-contents "input-test")
       (goto-char (point-min))
       (replace-regexp "^\\(#.*#\\)$" "\"\\1\"")
       (goto-char (point-min))
@@ -131,6 +131,7 @@ In the version below, we record dead-ends and partial solutions
                  (new-score (-min-by #'>nil (-map (lambda (newdir)
                                                     (explore (neighbour-maybe p dir newdir) newdir dir
                                                              (+ score (if (equal newdir dir) 1 1000))
+
                                                              (-distinct (cons p past))))
                                                   acceptable-dirs))))
             (when (not (eq new-score 'loop)) (push (cons (list p dir) (subtract-nil new-score score)) book))
@@ -141,6 +142,40 @@ In the version below, we record dead-ends and partial solutions
   #+end_src
 
 #+RESULTS:
-: 11048
+: 276920
+
+The above does not work for some reasons I do not fully understand.
+Let me try with a different approach.  Now we start from a point and a
+direction; we do one round of explorations and end up with a list of
+starting points, directions and accumulated scores.
+#+begin_src emacs-lisp
+  (setq start-vector (list start '(1 0) 0)) ; starting point, direction and score
+
+  (defun forward-dirs (dir)
+      (cons dir (--filter (= (dot it dir) 0) '((0 1) (0 -1) (-1 0) (1 0)))))
+
+  (defun explore (start-vect &optional stop)
+   (let* ((p (car start-vect))
+          (dir (cadr start-vect))
+          (score (caddr start-vect))
+          (acceptable-dirs (--filter (not (eq (thing-at (neighbour p it)) 'wall)) (forward-dirs dir))))
+     (if (and (> (length acceptable-dirs) 1) stop) (list start-vect)
+       (push p book)
+       (-mapcat (lambda (newdir) (explore (list (neighbour p newdir)
+                                                newdir
+                                                (+ score (if (equal newdir dir) 1 1000)))
+                                          t ))
+                acceptable-dirs))))
+
+  (setq book nil)
+
+  
+
+  (explore start-vector)
+#+end_src
+
+#+RESULTS:
+| (1 11) | (0 -1) | 1001 |
+
 
 (print-map)