[p22] part 1

p22/p22.org

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+#+title: Solution to p22
+
+#+begin_src emacs-lisp :results none
+  (require 'dash)
+  (with-temp-buffer
+      (insert-file-contents "input")
+      (goto-char (point-min))
+      (insert "(setq data '(")
+      (goto-char (point-max))
+      (insert "))")
+      (eval-buffer))
+#+end_src
+
+#+begin_src emacs-lisp :results none
+  (defun mix (a b)
+    (logxor a b))
+
+  (defun prune (a)
+    (logand a 16777215))
+
+  (defun pseudo-next-1 (a)
+    (prune (mix a (ash a 6))))
+
+  (defun pseudo-next-2 (a)
+    (prune (mix a (ash a -5))))
+
+  (defun pseudo-next-3 (a)
+    (prune (mix a (ash a 11))))
+
+  (defun pseudo-next (a)
+    (pseudo-next-3
+     (pseudo-next-2
+      (pseudo-next-1 a)))
+    )
+    #+end_src
+
+#+begin_src emacs-lisp 
+  (apply #'+ (--map (-last-item  (-iterate 'pseudo-next it 2001)) data))
+#+end_src
+
+#+RESULTS:
+: 19241711734