# What does **APX** mean in **File Extensions**?

## This page is about the meanings of the acronym/abbreviation/shorthand **APX** in the **Computing** field in general and in the **File Extensions** terminology in particular.

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# Definition

#### What does **APX** mean?

- APX
- In complexity theory the class APX is the set of NP optimization problems that allow polynomial-time approximation algorithms with approximation ratio bounded by a constant. In simple terms, problems in this class have efficient algorithms that can find an answer within some fixed percentage of the optimal answer. For example, there is a polynomial-time algorithm which will find a solution to the bin packing problem that uses at most 5% more than the smallest possible number of bins. An approximation algorithm is called a c-approximation algorithm for some constant c if it can be proven that the solution that the algorithm finds is at most c times worse than the optimal solution. Here, c is called the approximation ratio. Depending on whether the problem is a minimization or a maximization problem, this can either denote c times larger or c times smaller, respectively. For example, the vertex cover problem and traveling salesman problem with triangle inequality each have simple 2-approximation algorithms. In contrast, it's proven that the traveling salesman problem with arbitrary edge-lengths can not be approximated with approximation ratio bounded by a constant as long as the Hamiltonian-path problem can not be solved in polynomial time, that is unless P = NP.

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"APX." *Abbreviations.com.* STANDS4 LLC, 2014. Web. 23 Aug. 2014. <http://www.abbreviations.com/term/14647>.

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