[p10] Add some comments

p10/p10.org

@@ -1,5 +1,7 @@
 #+title: Solution to p10
 
+This problem is pretty hard. I have not yet completely understood the
+linear algebra behind it.
 #+begin_src emacs-lisp :results none
   (with-temp-buffer
     (insert-file-contents "input")
@@ -18,15 +20,19 @@
     (insert "))")
     (eval-buffer))
 #+end_src
-#+begin_src emacs-lisp :results none
+
+For part 1 we do not need the last item This is a linear algebra
+problem in characteristic 2; we are essentially bruteforcing the
+vector space; we easily succeed.
+#+begin_src emacs-lisp
   (defun zero-one (n)
     (if (eq n ?#) 1 0))
 
-  (setq cleanedup-data (--map (cons (-map #'zero-one (advent/split-string-into-char-list (car it))) (cdr it)) data))
-  #+end_src
+  (setq cleanedup-data (--map (cons (-map #'zero-one
+                                          (advent/split-string-into-char-list (car it)))
+                                    (cdr it))
+                              data))
 
-for part 1 we do not need the last item
-#+begin_src emacs-lisp
   (setq machines (--map (-drop-last 1 it) cleanedup-data))
 
   (defun to-bin (l)
@@ -35,18 +41,21 @@ for part 1 we do not need the last item
   (defun to-mask (l)
     (-sum (--map (expt 2 it) l)))
 
-  (setq mask-machines (--map (cons (to-bin (car it)) (-map #'to-mask (cdr it))) machines))
+  (setq mask-machines (--map (cons (to-bin (car it))
+                                   (-map #'to-mask (cdr it)))
+                             machines))
 
   (-sum
    (-map (lambda (machine)
-  	 (-min (-map 'length  (--filter (= (car machine) (apply 'logxor it))
-  					(-powerset (cdr machine))))))
+     (-min (-map 'length  (--filter (= (car machine) (apply 'logxor it))
+                    (-powerset (cdr machine))))))
          mask-machines))
 #+end_src
 
 #+RESULTS:
 : 7
 
+
 This approach blows the stack even for the test input
 #+begin_src emacs-lisp
   (setq machines (--map (-rotate 1 (cdr it)) data))
@@ -181,7 +190,7 @@ is a linear algebra problem.  Gauss elimination to the rescue
            (--map (advent/dot it vector) matrix))
 
          (defun solution-p (machine candidate)
-           (--every (= 0 it) (matrix-appl (matrix-buttons machine) (cons -1 candidate))) 
+           (--every (= 0 it) (matrix-appl (matrix-buttons machine) (cons -1 candidate)))
            )
        (setq current-machine nil)
          (defun solve--machine (machine)