From c0d8f3ef3c8fdc6a5797a305e6f7a099bd0b61fd Mon Sep 17 00:00:00 2001
From: Jacopo De Simoi <wilderjds@protonmail.com>
Date: Thu, 10 Apr 2025 07:46:23 -0400
Subject: [PATCH] add some explanations

---
 p10/p10.org | 25 ++++++++++++++-----------
 p11/p11.org | 10 +++++-----
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/p10/p10.org b/p10/p10.org
index 42b5191..e846529 100644
--- a/p10/p10.org
+++ b/p10/p10.org
@@ -18,7 +18,7 @@ Load the file into a list of lines
 
 #+RESULTS:
 
-and split into a list of list of chars
+and split into a list of list of heights, calculating height and width
 #+begin_src emacs-lisp
   (setq data-heights (-map (lambda (str) (--map (- (string-to-char it) ?0) (split-string str "\\|.+" t)))
 			 data)
@@ -29,16 +29,18 @@ and split into a list of list of chars
 #+RESULTS:
 : 41
 
+here we define some helper functions
 #+begin_src emacs-lisp
-    (defun acceptable-p (p)
-      (let ((x (car p))
-	    (y (cadr p)))
-	(and (>= x 0) (>= y 0) (< x width) (< y height)) ))
+  (defun acceptable-p (p)
+    (let ((x (car p))
+	  (y (cadr p)))
+      (and (>= x 0) (>= y 0) (< x width) (< y height)) ))
 
-    (defun neighbours (p)
-      (let ((x (car p))
-	    (y (cadr p)))
-	(-filter #'acceptable-p (-map (lambda (q) (list (+ x (car q)) (+ y (cadr q)))) '((+1 0) (-1 0) (0 1) (0 -1))))))
+  (defun neighbours (p)
+    (let ((x (car p))
+	  (y (cadr p)))
+      (-filter #'acceptable-p
+	       (-map (lambda (q) (list (+ x (car q)) (+ y (cadr q)))) '((+1 0) (-1 0) (0 1) (0 -1))))))
 
   (defun height (p)
     (nth (car p) (nth (cadr p) data-heights)))
@@ -47,8 +49,7 @@ and split into a list of list of chars
 #+RESULTS:
 : height
 
-
-this yields the coordinates of the 0s 
+This yields the coordinates of the trailheads 
 #+begin_src emacs-lisp
   (setq trail-heads (-map #'cadr
 	  (--filter (eq (car it) 0)
@@ -253,6 +254,8 @@ this yields the coordinates of the 0s
 | 22 | 40 |
 | 23 | 40 |
 | 24 | 40 |
+
+these follow the trails to the top, calculating the two properties of each trailhead 
 #+begin_src emacs-lisp
      (defun tails (p h)
        (when (eq (height p) h)
diff --git a/p11/p11.org b/p11/p11.org
index f51448e..aed21e5 100644
--- a/p11/p11.org
+++ b/p11/p11.org
@@ -1,12 +1,11 @@
 #+title: Solution for p11
 
 #+begin_src emacs-lisp
-    (setq data '(0 27 5409930 828979 4471 3 68524 170))
-;  (setq data '(125 17))
+  (setq data '(125 17))
 #+end_src
 
 #+RESULTS:
-| 0 | 27 | 5409930 | 828979 | 4471 | 3 | 68524 | 170 |
+| 125 | 17 |
 
 Define the auxiliary functions
 #+begin_src emacs-lisp
@@ -28,14 +27,15 @@ Define the auxiliary functions
  #+RESULTS:
  : blink
 
-And now compute
+And now compute. For the first step a simple implementation suffices
  #+begin_src emacs-lisp
    (length (-last-item  (--iterate (-mapcat #'blink it) data (1+ 25))))
  #+end_src
 
  #+RESULTS:
  : 194482
-
+ 
+Otherwise, we need to be smarter. We group Peebles in piles with the same engraving and blink only once for each group 
  #+begin_src emacs-lisp
    (setq freq-data (-frequencies data))