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How to prove that a problem is NP complete?

...least one vertex in the cover set?) is in NP: our input X is some graph G and some number k (this is from the problem definition) Take our information C to be "any possible subset of vertices in graph G of size k" Then we can write an algorithm V that, given G, k and C, will return whether that s...
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Why java.io.File doesn't have a close() method?

While java.io.RandomAccessFile does have a close() method java.io.File doesn't. Why is that? Is the file closed automatically on finalization or something? ...
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In Python, using argparse, allow only positive integers

... type would be the recommended option to handle conditions/checks, as in Yuushi's answer. In your specific case, you can also use the choices parameter if your upper limit is also known: parser.add_argument('foo', type=int, choices=xrange(5, 10)) Note: Use range ...
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How can I select multiple columns from a subquery (in SQL Server) that should have one record (selec

...es from the row with the highest value for Foo (rather than the max of Foo and the max of Foo2 - which is NOT the same thing) then the following will usually work better than a subquery: SELECT A.SalesOrderID, A.OrderDate, B1.Foo, B1.Foo2 FROM A LEFT OUTER JOIN B AS B1 ON ...
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Is it OK to use Gson instance as a static field in a model bean (reuse)?

...ginSession, so it should be static. GSON instances should be thread-safe, and there was a bug regarding that which was fixed. share | improve this answer | follow ...
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Removing packages installed with go get

...ullies my root Go install (I would much prefer to keep my Go install clean and separate core from custom). How do I remove packages installed previously? ...
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Map.clear() vs new Map : Which one will be better? [duplicate]

...h is backed with new array. So, garbage collector should clear all the key and values from the previous map, and clear the reference to itself. So O(n) algorithm is executed anyway, but in the garbage collector thread. For 1000 records you won't see any difference. BUT. The performance guide tells ...
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What does “@@ -1 +1 @@” mean in Git's diff output?

...:30:39.942229878 -0800 to indicate the date, time with fractional seconds, and time zone. The fractional seconds are omitted on hosts that do not support fractional time stamps. You can change the header's content with the --label=label option; see See Alternate Names. Next come one or mor...
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How to implement infinity in Java?

...X_VALUE field of the Integer class: Integer myInf = Integer.MAX_VALUE; (And for NEGATIVE_INFINITY you could use MIN_VALUE.) There will of course be some functional differences, e.g., when comparing myInf to a value that happens to be MAX_VALUE: clearly this number isn't less than myInf. There's ...
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How do I apply a perspective transform to a UIView?

...ws] objectAtIndex:0]; CALayer *layer = myView.layer; CATransform3D rotationAndPerspectiveTransform = CATransform3DIdentity; rotationAndPerspectiveTransform.m34 = 1.0 / -500; rotationAndPerspectiveTransform = CATransform3DRotate(rotationAndPerspectiveTransform, 45.0f * M_PI / 180.0f, 0.0f, 1.0f, 0.0f...