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Why do we check up to the square root of a prime number to determine if it is prime?
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If a number n is not a prime, it can be factored into two factors a and b:
n = a * b
Now a and b can't be both greater than the square root of n, since then the product a * b would be greater than sqrt(n) * sqrt(n) = n. So in any factorization of n, at least one of the factors must be smal...
Generate random int value from 3 to 6
Is it possible in Microsoft SQL Server generate random int value from Min to Max (3-9 example, 15-99 e.t.c)
10 Answers
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Spinlock versus Semaphore
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Spinlock and semaphore differ mainly in four things:
1. What they are
A spinlock is one possible implementation of a lock, namely one that is implemented by busy waiting ("spinning"). A semaphore is a generalization of a lock (or, th...
The modulo operation on negative numbers in Python
...but in C, if N ≥ 3, we get a negative number which is an invalid number, and we need to manually fix it up by adding 7:
int result = (2 - N) % 7;
return result < 0 ? result + 7 : result;
(See http://en.wikipedia.org/wiki/Modulo_operator for how the sign of result is determined for different la...
How to fetch the row count for all tables in a SQL SERVER database [duplicate]
... table_name varchar(255),
row_count int
)
EXEC sp_MSForEachTable @command1='INSERT #counts (table_name, row_count) SELECT ''?'', COUNT(*) FROM ?'
SELECT table_name, row_count FROM #counts ORDER BY table_name, row_count DESC
DROP TABLE #counts
The output will be a list of tables and their row ...
Add a column to existing table and uniquely number them on MS SQL Server
I want to add a column to an existing legacy database and write a procedure by which I can assign each record a different value. Something like adding a column and autogenerate the data for it.
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Switch statement fallthrough in C#?
... Damn - I've been programming with C# since the early days of 1.0, and I've never seen this until now. Just goes to show, you learn new things every day.
– Erik Forbes
Feb 5 '09 at 3:30
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powershell - extract file name and extension
I need to extract file name and extension from e.g. my.file.xlsx. I don't know the name of file or extension and there may be more dots in the name, so I need to search the string from the right and when I find first dot (or last from the left), extract the part on the right side and the part on the...
Visual Studio debugging/loading very slow
...") my ASP.NET MVC sites. Not always: at first, the projects will load nice and fast, but once they load slow, they'll always load slow after that. I could be waiting 1-2 minutes or more.
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Drawing a connecting line between two elements [closed]
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jsPlumb is an option available that supports drag and drop, as seen by its numerous demos, including the Flowchart demo.
It is available in a free Community edition, and a paid Toolkit edition.
The Toolkit edition wraps the Community edition with a comprehensive data bi...