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	<title>Carlos Vilhena&#039;s blog</title>
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		<title>Carlos Vilhena&#039;s blog</title>
		<link>http://vilhena.wordpress.com</link>
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		<title>Problem 107: Determining the most efficient way to connect a network</title>
		<link>http://vilhena.wordpress.com/2010/09/26/problem-107-determining-the-most-efficient-way-to-connect-a-network/</link>
		<comments>http://vilhena.wordpress.com/2010/09/26/problem-107-determining-the-most-efficient-way-to-connect-a-network/#comments</comments>
		<pubDate>Sun, 26 Sep 2010 20:02:53 +0000</pubDate>
		<dc:creator>carlosvilhena</dc:creator>
				<category><![CDATA[Algorithms]]></category>
		<category><![CDATA[Computing Science]]></category>
		<category><![CDATA[Project Euler]]></category>
		<category><![CDATA[Graphs]]></category>
		<category><![CDATA[Java]]></category>
		<category><![CDATA[linkedin]]></category>

		<guid isPermaLink="false">http://vilhena.wordpress.com/?p=234</guid>
		<description><![CDATA[The 107th Euler Problem aims to calculate the most efficient way to connect a given network. This is definitely a problem that can be solved using graphs, i.e. it&#8217;s a typical minimum spanning tree (MST) problem (Prim&#8217;s algorithm). Please note that the code below is just a snapshot of the original code. If one wants [...]<img alt="" border="0" src="http://stats.wordpress.com/b.gif?host=vilhena.wordpress.com&amp;blog=6454217&amp;post=234&amp;subd=vilhena&amp;ref=&amp;feed=1" width="1" height="1" />]]></description>
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		<title>Problem 59: Break the XOR cipher only with the cipher text</title>
		<link>http://vilhena.wordpress.com/2010/09/18/problem-59-break-the-xor-cipher-only-with-the-cipher-text/</link>
		<comments>http://vilhena.wordpress.com/2010/09/18/problem-59-break-the-xor-cipher-only-with-the-cipher-text/#comments</comments>
		<pubDate>Sat, 18 Sep 2010 13:51:22 +0000</pubDate>
		<dc:creator>carlosvilhena</dc:creator>
				<category><![CDATA[Cryptography]]></category>
		<category><![CDATA[Project Euler]]></category>
		<category><![CDATA[Haskell]]></category>
		<category><![CDATA[linkedin]]></category>

		<guid isPermaLink="false">http://vilhena.wordpress.com/?p=218</guid>
		<description><![CDATA[This problem is about breaking the XOR cipher using only the cipher text and having the following information: The key used to encrypt the original text has length 3; The key contains lower case characters. In such a simple encryption algorithm, it is actually possible to find the original text and the key by brute-force [...]<img alt="" border="0" src="http://stats.wordpress.com/b.gif?host=vilhena.wordpress.com&amp;blog=6454217&amp;post=218&amp;subd=vilhena&amp;ref=&amp;feed=1" width="1" height="1" />]]></description>
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		<slash:comments>0</slash:comments>
	
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			<media:title type="html">carlosvilhena</media:title>
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		<item>
		<title>Problem 56: Maximum digital sum of a googol</title>
		<link>http://vilhena.wordpress.com/2010/09/11/problem-56-maximum-digital-sum-of-a-googol/</link>
		<comments>http://vilhena.wordpress.com/2010/09/11/problem-56-maximum-digital-sum-of-a-googol/#comments</comments>
		<pubDate>Sat, 11 Sep 2010 15:56:54 +0000</pubDate>
		<dc:creator>carlosvilhena</dc:creator>
				<category><![CDATA[Computing Science]]></category>
		<category><![CDATA[Project Euler]]></category>
		<category><![CDATA[Haskell]]></category>
		<category><![CDATA[linkedin]]></category>

		<guid isPermaLink="false">http://vilhena.wordpress.com/?p=214</guid>
		<description><![CDATA[In order to solve this problem, I just created a brute force algorithm in Haskell: import List import Char result = maximum [g (a^b) &#124; a &#60;- [1..99], b &#60;- [1..99]] where g = sum . map digitToInt . show main = print $ result The execution is pretty fast: real 0m0.059s user 0m0.055s sys 0m0.003s<img alt="" border="0" src="http://stats.wordpress.com/b.gif?host=vilhena.wordpress.com&amp;blog=6454217&amp;post=214&amp;subd=vilhena&amp;ref=&amp;feed=1" width="1" height="1" />]]></description>
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		<slash:comments>0</slash:comments>
	
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			<media:title type="html">carlosvilhena</media:title>
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		<title>Problem 79: Determine online banking password based on successful attempts</title>
		<link>http://vilhena.wordpress.com/2010/09/11/problem-79-determine-online-banking-password-based-on-successful-attempts/</link>
		<comments>http://vilhena.wordpress.com/2010/09/11/problem-79-determine-online-banking-password-based-on-successful-attempts/#comments</comments>
		<pubDate>Sat, 11 Sep 2010 15:22:23 +0000</pubDate>
		<dc:creator>carlosvilhena</dc:creator>
				<category><![CDATA[Computing Science]]></category>
		<category><![CDATA[Cryptography]]></category>
		<category><![CDATA[Project Euler]]></category>
		<category><![CDATA[linkedin]]></category>

		<guid isPermaLink="false">http://vilhena.wordpress.com/?p=211</guid>
		<description><![CDATA[I solved the 79th Euler problem with pen and paper, since the input data was rather small (50 attempts, with repetitions). The ideia is to find the shortest possible secret passcode based on a log fie containing 50 successful login attempts. Furthermore, the characters are asked in order, which eases the process of finding the [...]<img alt="" border="0" src="http://stats.wordpress.com/b.gif?host=vilhena.wordpress.com&amp;blog=6454217&amp;post=211&amp;subd=vilhena&amp;ref=&amp;feed=1" width="1" height="1" />]]></description>
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		<slash:comments>0</slash:comments>
	
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			<media:title type="html">carlosvilhena</media:title>
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		<item>
		<title>QuickSort: Haskell vs C</title>
		<link>http://vilhena.wordpress.com/2010/07/04/quicksort-haskell-vs-c/</link>
		<comments>http://vilhena.wordpress.com/2010/07/04/quicksort-haskell-vs-c/#comments</comments>
		<pubDate>Sun, 04 Jul 2010 20:18:54 +0000</pubDate>
		<dc:creator>carlosvilhena</dc:creator>
				<category><![CDATA[Algorithms]]></category>
		<category><![CDATA[Computing Science]]></category>
		<category><![CDATA[Optimization]]></category>
		<category><![CDATA[C]]></category>
		<category><![CDATA[Haskell]]></category>
		<category><![CDATA[linkedin]]></category>
		<category><![CDATA[Profiling]]></category>

		<guid isPermaLink="false">http://vilhena.wordpress.com/?p=176</guid>
		<description><![CDATA[I was playing around with some sorting algorithms and I decided to try to compare the implementation of the QuickSort algorithm in Haskell and in C.<img alt="" border="0" src="http://stats.wordpress.com/b.gif?host=vilhena.wordpress.com&amp;blog=6454217&amp;post=176&amp;subd=vilhena&amp;ref=&amp;feed=1" width="1" height="1" />]]></description>
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		<slash:comments>0</slash:comments>
	
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			<media:title type="html">Screen shot 2010-07-04 at 9.27.34 PM</media:title>
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		<item>
		<title>Optimizing the Ackermann Function using Haskell &#8211; part 1</title>
		<link>http://vilhena.wordpress.com/2010/07/04/optimizing-the-ackermann-function-using-haskell-part-1/</link>
		<comments>http://vilhena.wordpress.com/2010/07/04/optimizing-the-ackermann-function-using-haskell-part-1/#comments</comments>
		<pubDate>Sun, 04 Jul 2010 12:23:30 +0000</pubDate>
		<dc:creator>carlosvilhena</dc:creator>
				<category><![CDATA[Computing Science]]></category>
		<category><![CDATA[Ackermann function]]></category>
		<category><![CDATA[Fix point]]></category>
		<category><![CDATA[Haskell]]></category>
		<category><![CDATA[memoization]]></category>

		<guid isPermaLink="false">http://vilhena.wordpress.com/?p=174</guid>
		<description><![CDATA[This article aims to be the first one of a series of articles concerning the optimization of the Ackermann function using Haskell.<img alt="" border="0" src="http://stats.wordpress.com/b.gif?host=vilhena.wordpress.com&amp;blog=6454217&amp;post=174&amp;subd=vilhena&amp;ref=&amp;feed=1" width="1" height="1" />]]></description>
		<wfw:commentRss>http://vilhena.wordpress.com/2010/07/04/optimizing-the-ackermann-function-using-haskell-part-1/feed/</wfw:commentRss>
		<slash:comments>0</slash:comments>
	
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			<media:title type="html">carlosvilhena</media:title>
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		<media:content url="http://projecteuler.net/images/symbol_sum.gif" medium="image">
			<media:title type="html">∑</media:title>
		</media:content>

		<media:content url="http://projecteuler.net/images/symbol_le.gif" medium="image">
			<media:title type="html">≤</media:title>
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			<media:title type="html">≤</media:title>
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		<title>Bash: generate file with N random integers</title>
		<link>http://vilhena.wordpress.com/2010/07/03/bash-generate-file-with-n-random-integers/</link>
		<comments>http://vilhena.wordpress.com/2010/07/03/bash-generate-file-with-n-random-integers/#comments</comments>
		<pubDate>Sat, 03 Jul 2010 22:45:24 +0000</pubDate>
		<dc:creator>carlosvilhena</dc:creator>
				<category><![CDATA[Computing Science]]></category>
		<category><![CDATA[bash]]></category>
		<category><![CDATA[random integers]]></category>

		<guid isPermaLink="false">http://vilhena.wordpress.com/?p=179</guid>
		<description><![CDATA[Random numbers generation (into file).<img alt="" border="0" src="http://stats.wordpress.com/b.gif?host=vilhena.wordpress.com&amp;blog=6454217&amp;post=179&amp;subd=vilhena&amp;ref=&amp;feed=1" width="1" height="1" />]]></description>
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		<slash:comments>1</slash:comments>
	
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			<media:title type="html">carlosvilhena</media:title>
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		<item>
		<title>Problem 182 – RSA encryption</title>
		<link>http://vilhena.wordpress.com/2010/05/31/problem-182/</link>
		<comments>http://vilhena.wordpress.com/2010/05/31/problem-182/#comments</comments>
		<pubDate>Mon, 31 May 2010 20:54:34 +0000</pubDate>
		<dc:creator>carlosvilhena</dc:creator>
				<category><![CDATA[Computing Science]]></category>
		<category><![CDATA[Cryptography]]></category>
		<category><![CDATA[Project Euler]]></category>
		<category><![CDATA[Haskell]]></category>
		<category><![CDATA[linkedin]]></category>
		<category><![CDATA[RSA]]></category>

		<guid isPermaLink="false">http://vilhena.wordpress.com/?p=169</guid>
		<description><![CDATA[Find the sum of all values of e, 1&#60;e&#60;φ(1009,3643) and gcd(e,φ)=1, so that the number of unconcealed messages for this value of e is at a minimum.<img alt="" border="0" src="http://stats.wordpress.com/b.gif?host=vilhena.wordpress.com&amp;blog=6454217&amp;post=169&amp;subd=vilhena&amp;ref=&amp;feed=1" width="1" height="1" />]]></description>
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		<slash:comments>0</slash:comments>
	
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			<media:title type="html">carlosvilhena</media:title>
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		<title>Problem 37</title>
		<link>http://vilhena.wordpress.com/2010/05/30/problem-37/</link>
		<comments>http://vilhena.wordpress.com/2010/05/30/problem-37/#comments</comments>
		<pubDate>Sun, 30 May 2010 09:49:26 +0000</pubDate>
		<dc:creator>carlosvilhena</dc:creator>
				<category><![CDATA[Computing Science]]></category>
		<category><![CDATA[Project Euler]]></category>
		<category><![CDATA[Haskell]]></category>
		<category><![CDATA[linkedin]]></category>
		<category><![CDATA[Prime numbers]]></category>

		<guid isPermaLink="false">http://vilhena.wordpress.com/?p=162</guid>
		<description><![CDATA[In the 37th Euler problem, I used the Hackage package containing the NumberTheory.Sieve.ONeill library in order to have access to an efficient infinite list of primes. Then it was a matter of manipulating lists to achieve the result. import NumberTheory.Sieve.ONeill import List import Char myElem (x:xs) n &#124; n == x = True &#124; n [...]<img alt="" border="0" src="http://stats.wordpress.com/b.gif?host=vilhena.wordpress.com&amp;blog=6454217&amp;post=162&amp;subd=vilhena&amp;ref=&amp;feed=1" width="1" height="1" />]]></description>
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		<slash:comments>0</slash:comments>
	
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		<title>Problem 36</title>
		<link>http://vilhena.wordpress.com/2010/05/30/problem-36/</link>
		<comments>http://vilhena.wordpress.com/2010/05/30/problem-36/#comments</comments>
		<pubDate>Sun, 30 May 2010 09:36:32 +0000</pubDate>
		<dc:creator>carlosvilhena</dc:creator>
				<category><![CDATA[Computing Science]]></category>
		<category><![CDATA[Project Euler]]></category>
		<category><![CDATA[Haskell]]></category>
		<category><![CDATA[linkedin]]></category>
		<category><![CDATA[Palindrome]]></category>

		<guid isPermaLink="false">http://vilhena.wordpress.com/?p=160</guid>
		<description><![CDATA[Below, one can find my solution to the 36th Euler problem: import Numeric import Char import List f i = isPalindrome (show i) &#38;&#38; isPalindrome (showIntAtBase 2 intToDigit i "") where isPalindrome l = l == reverse l main = print $ sum [i &#124; i &#60;- [1..10^6], f i] GHC&#8217;s execution time was good [...]<img alt="" border="0" src="http://stats.wordpress.com/b.gif?host=vilhena.wordpress.com&amp;blog=6454217&amp;post=160&amp;subd=vilhena&amp;ref=&amp;feed=1" width="1" height="1" />]]></description>
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