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Fast permutation -> number -> permutation mapping algorithms
... In general, the k'th digit will have base b[k] = k + 2. The highest value allowed for digit k is h[k] = b[k] - 1 = k + 1.
Our rule about the weights w[k] of digits requires that the sum of h[i] * w[i], where i goes from i = 0 to i = k, is equal to 1 * w[k+1]. Stated recurrently, w[k+1] = w[k] + h[...
Update all values of a column to lowercase
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@BjörnC - upper/lower only changes letters; all other characters are unchanged.
– ToolmakerSteve
Apr 9 '19 at 17:54
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When to use DataContract and DataMember attributes?
...tes, with .NET 3.5 SP1, Microsoft made the data contract serializer handle all classes - even without any of those attributes - much like the old XML serializer.
So as of .NET 3.5 SP1, you don't have to add data contract or data member attributes anymore - if you don't then the data contract serial...
Using an HTML button to call a JavaScript function
I am trying to use an HTML button to call a JavaScript function.
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How to get duplicate items from a list using LINQ? [duplicate]
...t; s)
.SelectMany(grp => grp.Skip(1));
Note that this will return all duplicates, so if you only want to know which items are duplicated in the source list, you could apply Distinct to the resulting sequence or use the solution given by Mark Byers.
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Fastest way to check if a file exist using standard C++/C++11/C?
...e thousands of files and before doing something on them I need to check if all of them exist. What can I write instead of /* SOMETHING */ in the following function?
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Why are arrays of references illegal?
...question about standard I can cite the C++ Standard §8.3.2/4:
There shall be no references to references, no arrays of references, and no pointers to references.
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How do ACID and database transactions work?
... achieve the ACID properties.
Atomicity means that you can guarantee that all of a transaction happens, or none of it does; you can do complex operations as one single unit, all or nothing, and a crash, power failure, error, or anything else won't allow you to be in a state in which only some of th...
How to delete a stash created with git stash create?
...e nothing references the stash commit, it will get garbage collected eventually.
A stash created with git stash or git stash save is saved to refs/stash, and can be deleted with git stash drop. As with all Git objects, the actual stash contents aren't deleted from your computer until a gc prunes ...
How to drop a PostgreSQL database if there are active connections to it?
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Actually it would disconnect clients one by one, and if you client is in the middle of the list it will be disconnected too. As a result, some connections will stay alive. So, the right answer is by Craig Ringer (see below). SELE...