#Vector td easy code#

Int **ptrConc // initialized to via new and destructed via delete Given the following declarations: int cConc

A multidimensional std::vector will not be packed in all dimensions. A multidimensional std::array will have the elements packed in memory in all dimensions, just as a C style array is. If you are considering using multidimensional arrays, then there is one additional difference between std::array and std::vector. If any of those requirements is not true, then use a std::vector.

the lifetime is in the function scope (or is a member value with the same lifetime as the parent class)ĭefinitely use a std::array over a vector.

#Vector td easy code#

small 'array' (under 100 elements say) - (a typical stack is about 8MB, so don't allocate more than a few KB on the stack or less if your code is recursive).

To be sure, std::array won't always be on the stack it depends on where you allocate it, but it will still involve one less memory allocation from the heap compared to vector. The stack also avoids memory fragmentation. Stack memory (possible for array) is virtually 'zero-overhead' in terms of time, because the memory is allocated by just adjusting the stack pointer and it is done just once on entry to a function. Heap memory (required with vector) requires a call to the system to allocate memory and this can be expensive if you are counting cycles. To emphasize a point made by the efficiency difference is where the data is stored. As stated by the standard actually requires that the elements are stored contiguously, so it is a dynamic array, stored where the associated allocator puts it. random access in constant time, iteration over all the elements in linear time, add and removal of elements at the end in constant amortized time, etc), but AFAIK there's no other method of fulfilling such requirements other than using a dynamic array.

Actually, I think that in the standard they are described in terms of maximum complexity of the different operations (e.g.

Anyhow, for the very limitation of fixed size it's much less flexible than std::vector.įor an introduction to std::array, have a look at this article for a quick introduction to std::vector and to the the operations that are possible on it, you may want to look at its documentation.

However, it's more secure, since the implicit conversion to pointer is disabled, and it provides much of the STL-related functionality of std::vector and of the other containers, so you can use it easily with STL algorithms & co. It's more limited than std::vector, but it's often more efficient, especially for small sizes, because in practice it's mostly a lightweight wrapper around a C-style array. Its size has to be known at compile time (it's passed as a template parameter), and it cannot grow or shrink.

Std::array is a template class that encapsulate a statically-sized array, stored inside the object itself, which means that, if you instantiate the class on the stack, the array itself will be on the stack. Since it stores the elements in memory allocated on the heap, it has some overhead in respect to static arrays. inserting elements in the middle of a vector (it handles all the work of moving the following elements behind the scenes). It also has several useful methods that let you perform operations that on a normal array would be cumbersome, like e.g. It provides all the hooks ( begin(), end(), iterators, etc) that make it work fine with the rest of the STL. Std::vector is a template class that encapsulate a dynamic array 1, stored in the heap, that grows and shrinks automatically if elements are added or removed.