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IBM Research: Ponder This - http://researchweb.watson.ibm.com/ponder/
Monthly logic and math puzzles set by IBM researchers with solutions. |
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TechInterview - http://www.techinterview.org/
Answers to technical interview questions, programming problems, and brain teasers. |
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Jim Loy's Puzzle Page - http://www.jimloy.com/puzz/puzz.htm
Classic and original puzzles. |
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Perplexus - http://perplexus.info/
A forum and collection of brain teasers, logic problems, math problems, paradoxes, science games, probability, riddles, and geometric shapes. The puzzles are searchable and categorized, most have solutions. |
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Kakuro-san - http://www.kakurosan.com
Providing graded Kakuro puzzles every day, plus old puzzles. |