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Time complexity of Sieve of Eratosthenes algorithm
...cals of all numbers up to n), which is O(n log n): see Harmonic number. A more proper upper-bound is n(1/2 + 1/3 + 1/5 + 1/7 + …), that is sum of reciprocals of primes up to n, which is O(n log log n). (See here or here.)
The "find the next prime number" bit is only O(n) overall, amortized — yo...
Remove file from the repository but keep it locally
I have a folder which I'd like to remove in my remote repository. I'd like to delete it, but keep the folder in my computer
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How to get String Array from arrays.xml file
...an array that I have in my arrays.xml . When I try to run it in the emulator, I get a force close message.
3 Answers
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Find all files with a filename beginning with a specified string?
I have a directory with roughly 100000 files in it, and I want to perform some function on all files beginning with a specified string, which may match tens of thousands of files.
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How to skip “are you sure Y/N” when deleting files in batch files
I can't for the life of me remember how to bypass the annoying prompt are you sure? Y/N when deleting files.
4 Answers
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Rails: update_attribute vs update_attributes
...te. On clicking show source you will get following code
# File vendor/rails/activerecord/lib/active_record/base.rb, line 2614
2614: def update_attribute(name, value)
2615: send(name.to_s + '=', value)
2616: save(false)
2617: end
and now refer update_attributes a...
How do I compare two string variables in an 'if' statement in Bash? [duplicate]
I'm trying to get an if statement to work in Bash (using Ubuntu ):
12 Answers
12
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Java: Path vs File
For new applications written in Java 7, is there any reason to use a java.io.File object any more or can we consider it deprecated?
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What is the purpose of setting a key in data.table?
...set a key (e.g. X[Y] ). As such, I wish to understand what a key does in order to properly set keys in my data tables.
2 ...
How do I automatically sort a has_many relationship in Rails?
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You can specify the sort order for the bare collection with an option on has_many itself:
class Article < ActiveRecord::Base
has_many :comments, :order => 'created_at DESC'
end
class Comment < ActiveRecord::Base
belongs_to :artic...