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Why does Dijkstra's algorithm use decrease-key?
... the total number of heap dequeues is n. Each node will have decrease-key called on it potentially once for each edge leading into it, so the total number of decrease-keys done is at most m. This gives a runtime of (n Te + n Td + m Tk), where Tk is the time required to call decrease-key.
So what ...
Adding 'serial' to existing column in Postgres
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You can also use START WITH to start a sequence from a particular point, although setval accomplishes the same thing, as in Euler's answer, eg,
SELECT MAX(a) + 1 FROM foo;
CREATE SEQUENCE foo_a_seq START WITH 12345; -- replace ...
Find XOR of all numbers in a given range
You are given a large range [a,b] where 'a' and 'b' can be typically between 1 and 4,000,000,000 inclusive. You have to find out the XOR of all the numbers in the given range.
...
Foreign keys in mongo?
...ot 'tables' but collections. Documents are grouped inside Collections. You can have any kind of document – with any kind of data – in a single collection. Basically, in a NoSQL database it is up to you to decide how to organise the data and its relations, if there are any.
What Mongoid and Mong...
When do I need to use a semicolon vs a slash in Oracle SQL?
...L object, running a PL/SQL anonymous block, and executing a DML statement) can be picked out more easily by eye.
Also, if you eventually move to something like Ant for deployment it will simplify the definition of targets to have a consistent statement delimiter.
...
Skip a submodule during a Maven build
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Sure, this can be done using profiles. You can do something like the following in your parent pom.xml.
...
<modules>
<module>module1</module>
<module>module2</module>
...
</m...
using gitignore to ignore (but not delete) files
...l tells me about changes to files in that directory. I tried git rm -r --cached , but that removes it from the remote repo. How can I stop tracking changes to this directory, but still allow it to exist? I also need to do this for 1 file, but changes to that also show up in git status after ....
Python - write() versus writelines() and concatenated strings
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More specifically, writelines expects an iterable. You can use a list, a tuple, or a generator.
– Mark Ransom
Sep 11 '12 at 20:52
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What's the difference between an exclusive lock and a shared lock?
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I wrote this answer down because I thought this would be a fun (and fitting) analogy:
Think of a lockable object as a blackboard (lockable) in a class room containing a teacher (writer) and many students (readers).
While a teacher is writing somethin...
Difference between size_t and std::size_t
... common mistake
is to assume size_t is the same as
unsigned int, which can lead to
programming errors,[3][4] when moving
from 32 to 64-bit architecture, for
example.
According to the 1999 ISO C
standard (C99), size_t is an unsigned
integer type of at least 16 bits.
And the rest ...