std::vector::reserve

 

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void reserve( size_type new_cap );

Increase the capacity of the container to a value that's greater or equal to new_cap. If new_cap is greater than the current capacity(), new storage is allocated, otherwise the method does nothing.

If new_cap is greater than capacity(), all iterators and references, including the past-the-end iterator, are invalidated. Otherwise, no iterators or references are invalidated.

Parameters

new_cap	-	new capacity of the container
Type requirements
- T must meet the requirements of MoveInsertable.

Return value

(none)

Exceptions

std::length_error if new_cap > max_size().

Complexity

At most linear in the size() of the container.

Notes

reserve() cannot be used to reduce the capacity of the container, to that end shrink_to_fit() is provided.

See also

capacity	returns the number of elements that can be held in currently allocated storage (public member function)
resize	changes the number of elements stored (public member function)
shrink_to_fit (C++11)	reduces memory usage by freeing unused memory (public member function)