Christian Lawson-Perfect christianp

How do you convert a stream of digits in one base into a stream of digits in another base?

Written up on my blog at http://checkmyworking.com/2012/06/converting-a-stream-of-binary-digits-to-a-stream-of-base-n-digits/

A card trick based on a de Bruijn sequence

Encode cards as 6-digit binary strings. Arrange them following a de Bruijn sequence. Get someone to draw 6 cards, and tell you their colours. You can tell them exactly which cards they have.

Written up on The Aperiodical at http://aperiodical.com/2012/08/davids-de-bruijn-sequence-card-trick/

	digraph{
	overlap=false;
	splines=true;
	"d0" [label="0"];
	"d1" [label="1"];
	"d2" [label="2"];
	"d4" [label="4"];
	"d16" [label="16"];
	"d37" [label="37"];
	"d58" [label="58"];

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	import sys
	import pickle
	import operator
	import itertools

	alphabet = 'abcdefghijklmnopqrstuvwxyz'

	#test if a word uses letters at most once
	def monoglyphic(word):
	word = sorted(word)

	#!/bin/sh
	EDITOR_PATH=/srv/www/numbas.mas.ncl.ac.uk80/numbas/
	PYTHON=python2.6
	echo "Updating Numbas"
	cd /srv/numbas/dist
	git pull
	echo "Updating editor"
	cd $EDITOR_PATH
	git pull
	$PYTHON manage.py syncdb

	Regular expressions are equivalent to finite state automata. (well, lookahead needs a pushdown automaton, but that's OK)
	Describe password constraints using regular expressions.
	Randomly traverse the FSA corresponding to a password constraint. A path ending in an accepting state is a valid password.

	@echo off
	IF %1==north cd ..
	IF not %1==north cd %*