[p8] done parts 1 and 2

p8/p8.org

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+#+title: Solution to p8
+
+#+begin_src emacs-lisp :results none
+  (with-temp-buffer
+    (insert-file-contents "input")
+    (advent/replace-multiple-regex-buffer
+     '(("," . " ")
+       ("^" . "(")
+       ("$" . ")")))
+    (goto-char (point-min))
+    (insert "(setq data '(")
+    (goto-char (point-max))
+    (insert "))")
+    (eval-buffer))
+#+end_src
+
+First of all, sort the pair of boxes by means of their distance.
+#+begin_src emacs-lisp :results none
+  (defun square (x)
+    (* x x))
+
+  (defun distance-squared (el)
+   (let ((a (car el))
+         (b (cdr el)))
+     (+ (square (- (car a) (car b)))
+        (square (- (cadr a) (cadr b)))
+        (square (- (caddr a) (caddr b))))))
+
+  (defun symmetric-pairs (list)
+   (apply #'append (--map-indexed (-map (lambda (other) (cons it other))
+                         (-drop (1+ it-index) list))
+                   list)))
+
+  (setq sorted-pairs
+        (--sort (< (distance-squared it) (distance-squared other)) (symmetric-pairs data)))
+#+end_src
+
+This is for part 1
+#+begin_src emacs-lisp
+  (defun insert-pair (circuits el)
+    (let* ((list (list (car el) (cdr el)))
+           (ind-a (--find-index (-contains-p it (car el)) circuits))
+           (ind-b (--find-index (-contains-p it (cdr el)) circuits)))
+      (cond
+       ((not (or ind-a ind-b)) (cons list circuits))
+       ((and ind-a ind-b (not (eq ind-a ind-b)))
+        (-remove-at ind-b (-replace-at ind-a
+                                       (-union (nth ind-a circuits)
+                                               (nth ind-b circuits))
+                                       circuits)))
+       (t  (-replace-at (or ind-a ind-b)
+                        (-union list (nth (or ind-a ind-b) circuits))
+                        circuits)))))
+
+  (setq circuits
+        (-reduce-from #'insert-pair nil (-take 1000 sorted-pairs)))
+
+  (-product (-take 3 (-sort '> (-map #'length circuits))))
+#+end_src
+
+#+RESULTS:
+: 81536
+
+This is for part 2. Will it explode?
+#+begin_src emacs-lisp
+  (let ((sorted-pairs sorted-pairs)
+        (circuits nil)
+        (last-junction nil))
+    (while (or (> 1 (length circuits))
+               (> (length data) (length (apply 'append circuits))))
+      (setq last-junction (pop sorted-pairs)
+            circuits (insert-pair circuits last-junction)))
+    last-junction
+    ;(* (caar last-junction) (cadr last-junction))
+    )
+
+
+
+#+end_src
+
+#+RESULTS:
+| (84981 85692 23226) | 91121 | 84159 | 34357 |