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Nearly all binary searches and mergesorts are broken (2006)
Posted by Joshua Bloch, Software EngineerI remember vividly Jon Bentley's first Algorithms lecture at CMU, where he asked all of us incoming Ph.D. ...
I remember vividly Jon Bentley's first Algorithms lecture at CMU, where he asked all of us incoming Ph.D. students to write a binary search, and then dissected one of our implementations in front of the class. Specifically, it fails if the sum of low and high is greater than the maximum positive int value (2 31- 1). Update 17 Feb 2008: Thanks to Antoine Trux, Principal Member of Engineering Staff at Nokia Research Center Finland for pointing out that the original proposed fix for C and C++ (Line 6), was not guaranteed to work by the relevant C99 standard (INTERNATIONAL STANDARD - ISO/IEC - 9899 - Second edition - 1999-12-01, 3.4.3.3), which says that if you add two signed quantities and get an overflow, the result is undefined.
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