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Difference between sh and bash
When writing shell programs, we often use /bin/sh and /bin/bash . I usually use bash , but I don't know what's the difference between them.
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Is log(n!) = Θ(n·log(n))?
...og(n) + log(n) + ... + log(n)
= n*log(n)
And you can get the lower bound by doing a similar thing after throwing away the first half of the sum:
log(1) + ... + log(n/2) + ... + log(n) >= log(n/2) + ... + log(n)
= log(n/2) ...
Computational complexity of Fibonacci Sequence
I understand Big-O notation, but I don't know how to calculate it for many functions. In particular, I've been trying to figure out the computational complexity of the naive version of the Fibonacci sequence:
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What characters are allowed in an email address?
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See RFC 5322: Internet Message Format and, to a lesser extent, RFC 5321: Simple Mail Transfer Protocol.
RFC 822 also covers email addresses, but it deals mostly with its structure:
addr-spec = local-part "@" domain ; global address
local-part ...
How to validate an email address using a regular expression?
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The fully RFC 822 compliant regex is inefficient and obscure because of its length. Fortunately, RFC 822 was superseded twice and the current specification for email addresses is RFC 5322. RFC 5322 leads to a regex that can be understood if studied for a few minutes and i...
Converting JSONarray to ArrayList
I am downloading a JSON string and converting it to JSONArray. Im putting it into a listview and need to be able to delete from that listview later, and since JSONArray has no .remove method (Thanks Obama), I am trying to convert it to an arraylist.
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How to find the kth largest element in an unsorted array of length n in O(n)?
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This is called finding the k-th order statistic. There's a very simple randomized algorithm (called quickselect) taking O(n) average time, O(n^2) worst case time, and a pretty complicated non-randomized algorithm (called introselect) taking O(n) worst case time. There's some info on Wikipedia, bu...
What is the difference between Θ(n) and O(n)?
...I see Θ(n) with the strange Θ symbol with something in the middle of it, and sometimes just O(n). Is it just laziness of typing because nobody knows how to type this symbol, or does it mean something different?
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Are 2^n and n*2^n in the same time complexity?
... answer this question.
The definition is that f(x) belongs to O(g(x)) if and only if the limit limsupx → ∞ (f(x)/g(x)) exists i.e. is not infinity. In short this means that there exists a constant M, such that value of f(x)/g(x) is never greater than M.
In the case of your question let f(n) ...
Code Golf: Collatz Conjecture
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x86 assembly, 1337 characters
;
; To assemble and link this program, just run:
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; >> $ nasm -f elf collatz.asm && gcc -o collatz collatz.o
;
; You can then enjoy its output by passing a number to it on the command line:
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; >> $ ./collatz 123
; >&...