http://sixrevisions.com/resources/10-puzzle-websites-to-sharpen-your-programming-skills/
http://www.coderholic.com/10-more-puzzle-websites-to-sharpen-your-programming-skills/
http://comeoncodeon.wordpress.com/page/2/
http://www.iarcs.org.in/inoi/contests/allproblems.php
https://www.interviewstreet.com/challenges/
https://www.facebook.com/ProgrammingInterviews
http://blog.seattleinterviewcoach.com/2009/02/140-google-interview-questions.html
http://www.cse.iitd.ernet.in/~sbaswana/Puzzles/Algo/algo.html
http://www.comp.nus.edu.sg/~stevenha/programming/vol1.html
http://www1.cs.columbia.edu/~kns10/interview/
http://concentratedlemonjuice.blogspot.com/2008/05/puzzles_4358.html
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