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Fast permutation -> number -> permutation mapping algorithms
...you have n possibilities, so you can describe this with a number between 0 and n-1. For the position that the next element ends up at, you have n-1 remaining possibilities, so you can describe this with a number between 0 and n-2.
Et cetera until you have n numbers.
As an example for n = 5, consid...
Why does the expression 0 < 0 == 0 return False in Python?
...
I believe Python has special case handling for sequences of relational operators to make range comparisons easy to express. It's much nicer to be able to say 0 < x <= 5 than to say (0 < x) and (x <= 5).
These are called chained comparisons. And th...
What's the difference between ASCII and Unicode?
What's the exact difference between Unicode and ASCII?
9 Answers
9
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CPU Privilege Rings: Why rings 1 and 2 aren't used?
...the modern protection model) only has a concept of privileged (ring 0,1,2) and unprivileged, the benefit to rings 1 and 2 were diminished greatly.
The intent by Intel in having rings 1 and 2 is for the OS to put device drivers at that level, so they are privileged, but somewhat separated from the r...
Delete topic in Kafka 0.8.1.1
... Thanks for the info. Do you know how to clear the entire Kafka and Zookeeper states as indicated?
– EmPak5
Jun 18 '14 at 16:09
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What values should I use for CFBundleVersion and CFBundleShortVersionString?
This is my first iOS app submission and I don't want my app rejected.
7 Answers
7
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SQL JOIN and different types of JOINs
What is a SQL JOIN and what are different types?
6 Answers
6
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When should I use cross apply over inner join?
...NER JOIN condition.
You could probably do something like that using CTE's and window function:
WITH t2o AS
(
SELECT t2.*, ROW_NUMBER() OVER (PARTITION BY t1_id ORDER BY rank) AS rn
FROM t2
)
SELECT t1.*, t2o.*
FROM t1
INNER JOIN
t2o
ON t2o.t1...
“Conversion to Dalvik format failed with error 1” on external JAR
In my Android application in Eclipse I get the following error.
71 Answers
71
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NumPy: function for simultaneous max() and min()
numpy.amax() will find the max value in an array, and numpy.amin() does the same for the min value. If I want to find both max and min, I have to call both functions, which requires passing over the (very big) array twice, which seems slow.
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