Container correct? This answer would be better if you made a clearer distinction about default construction vs value construction. In the constructor bit you cited, the vector value constructs, despite the implication that it default constructs, which is super annoying. MooingDuck I won't repeat here what is explained in great detail already in many places.
However, I did add more information to show that a custom allocator can be used to achieve default initialization. John D. Cook John D. Cook Yes, but if you want to mess with vector's internal stuff, there would be less advantage in using a vector. By the way, the keyword was "might not. The specific scenario in my mind when I wrote that was stack-based arrays.
Interfacing vector or any contiguous container with C: vec. It's that easy. Show 1 more comment. Juan Juan. This is important to mention. Profiling debug STL stuff is very, very slow. And it's one of the reasons why people thing STL is slow. Timo Geusch Timo Geusch Certainly this is the obvious way to do it. Not just the performance requirements, but also the requirement that storage in contiguous.
A bad vector implementation will put too many layers of indirection between the array and the API. A good vector implementation will allow for inlined code, SIMD used on loops, etc. A bad vector implementation as described would not be compliant with the standard. If you want indirection, std::deque might be used. If you're using vectors to represent multi-dimensional behavior, there is a performance hit. Seph Reed Seph Reed 5, 8 8 gold badges 34 34 silver badges 73 73 bronze badges.
Greg Rogers Greg Rogers Mark Ransom Mark Ransom k 40 40 gold badges silver badges bronze badges. Gabriel Isenberg Gabriel Isenberg Brian Brian If this matters, then you're obviously not using dynamically-sized arrays, and as such, your arrays don't need to change size.
If they did, you'd be storing the size somehow. Therefore, you might as well use boost::array unless I'm mistaken - and what makes you say that that needs to "store the size" somewhere? Hamed Hamed 51 3 3 bronze badges. This code was posted to comp. Obsidian 2, 7 7 gold badges 15 15 silver badges 27 27 bronze badges.
Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Explaining the semiconductor shortage, and how it might end. Does ES6 make JavaScript frameworks obsolete? Featured on Meta. Now live: A fully responsive profile. Linked 0. See more linked questions. Related Increasing a reverse iterator moves it towards the beginning of the container. This method passes an array to the constructor of the vector class.
The passed array contains the elements which will populate the vector. This method passes the begin and end iterators of an already initialized vector to a vector class constructor. A new vector is initialized and populated by the elements in the old vector. Join a community of , monthly readers.
A free, bi-monthly email with a roundup of Educative's top articles and coding tips. All rights reserved. I don't need to be told about the differences between the two data structures; I'm very aware of them. Also, regardless of what you think of the author's advice, what do you see in the real-world more often? A: Almost always [use a vector instead of an array].
That meant that even for types where construction was deliberately left as a no-operation, there was still a cost to copy the data elements - replicating their whatever-garbage-was-left-in-memory values. Clearly an array of uninitialised elements is faster. For better or worse, many such protocols often embed small fixed sized arrays. That said, if it's not an active pain to use a vector in code concision, readability or performance then you're better off doing so: they've size , checked random access via at , iterators, resizing which often becomes necessary as an application "matures" etc..
One of the best reasons to use a vector as opposed to an array is the RAII idiom. These objects should have destructors that free these resources. When an exception goes unhandled, the ONLY things that are gaurenteed to be called are the destructors of objects on the stack.
If you dynamically allocate memory outside of an object, and an uncaught exception is thrown somewhere before it is deleted, you have a memory leak.
You should also check out std::algorithm , which provides a lot of common algorithms for vector and other STL containers. I have on a few occasions written code with vector that, in retrospect, probably would have been better with a native array. A std::vector is just a resizable array. It's not much more than that. It's not something you would learn in a Data Structures class, because it isn't an intelligent data structure. In the real world, I see a lot of arrays.
The array allows both kinds of access, direct and sequential, while Vector only allows sequential access. And this is because of the way these data structures are stored in memory. Since Vector elements are placed in a contiguous memory block, they can be easily traversed using an iterator. An Array is very much tied to the hardware notion of continuous, contiguous memory, with each element identical in size.
At the end of the day, it all boils down to the requirement. A developer needs to weigh down the project requirement and thus make any decision. Here we also discuss the key differences with infographics and comparison table. Submit Next Question.
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