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Questions tagged [deque]

A double-ended queue. Container datatype which is typically supporting efficient insertion and removal from two ends.

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Add to a deque being iterated in Python?

I have a deque in Python that I'm iterating over. Sometimes the deque changes while I'm interating which produces a RuntimeError: deque mutated during iteration. If this were a Python list instead of a deque, I would just iterate over a copy of the…
Brian Madden
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dumping queue into list/array in python

I am running a number of threads and collecting there result on a queue. I would like to dump it into array or list so that I can do indexing and retrieve those results. Each of the elements in the queue is a array of dimension n. I would like to…
thetna
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time complexity of random access in deque in Python

I am wondering about the time complexity of the get operation of deque in Python. I know that it is implemented as a doubly link in Python. Does that mean that its time complexity is O(n)?
DSKim
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Why are deque's pop_front() and pop_back() not noexcept?

Is there any reason that std::deque's pop_front() and pop_back() are not noexcept in C++11 and higher or was that just forgotten?
Benjamin Buch
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deque remove item by index

Is there any way to remove an item in deque by index? dq = deque(['a','b','c']) dq.removeByIndex(1) #output deque(['b', 'c']) I only see remove by value in the doc. Also, I know I can just pop it i times and then put it back, but it doesn't look…
Denly
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How can I get the first value of a deque without deleting it?

I use Python 3.6.1 and I use deque() from collections quite often due to its convenience. This time, I need to get the first value of a deque and wonder if it's possible. The problem is that I can do that using .popleft(), but it ends up deleting…
maynull
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Confusion on iterators invalidation in deque

I'm bit confused regarding iterator invalidation in deque. (In the context of this question) Following is the excerpts from -- The C++ Standard Library: A Tutorial and Reference, By Nicolai M. Josuttis Any insertion or deletion of elements …
aJ.
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C++ std::deque implementation: why not use circular buffer?

I did some search on the implementation of deque. According to this post, deque uses vector of vectors. I know pushing at the begin and end should be both in constant time, and also random access is required. I think circular buffer meets all these…
sunnior
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Why is python deque initialized using the last maxlen items in an iterable?

I was learning how to use deque. Here's what I did: >>> d = deque([1,2,3,4,5,6], maxlen=3) I expected that d would contain [1,2,3]. But instead I got: >>> d deque([4, 5, 6], maxlen=3) Isn't this counterintuitive?
Haiyang
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dequeueReusableCellWithReuseIdentifier crash 'could not dequeue a view of kind" UICollectionElementKindCell'

I am getting the following crash: Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'could not dequeue a view of kind: UICollectionElementKindCell with identifier Cell - must register a nib or a class for the…
Ken Roy
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How to implement deque data structure in javascript?

I'm Learning data structure with javascript and my focus now on how to implement deque? Edite: from comments below I get useful directions on how to implement deque based array. Is there a direction how to implement deque based object using class…
Ayman Morsy
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Java equivalent of std::deque

I'm a relatively new Java programmer coming from C++/STL, and am looking for a class with these characteristics (which the C++ std::deque has, as I understand it): O(1) performance for insertion/removal at the beginning/end O(1) performance for…
Jason S
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Creating an empty deque in Python with a max length?

I'm looking at the documentation for a Python deque, and it looks like the constructor is deque([iterable[, maxlen]]). Is there no way to make an empty deque (that is, without specifying the iterable) with a max length?
itsmichaelwang
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Deque random acces O(n) in python while O(1) in C++, why?

C++ deque: Random access - constant O(1) Python deque: Indexed access is O(1) at both ends but slows to O(n) in the middle. If I'm not missing anything, everything else is equally fast for deques in python and in C++, at least complexity-wise.…
Typical User
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Is using std::deque or std::priority_queue thread-safe?

Possible Duplicates: Is the C++ STL std::set thread-safe? Thread safety for STL queue I'm guessing it isn't, I just want to make sure. meaning 2 threads using the same std::deque using std::deque::push_back or push_front at the same time. Same…
grich
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