How to Efficiently Create a Subvector in C ?

Creating a Subvector from a Vector

In C , if you have an existing vector of size N (myVec), and you wish to extract a subvector from it comprising elements from index X to index Y inclusive, the most straightforward method is to:

vector<T>::const_iterator first = myVec.begin() + X;
vector<T>::const_iterator last = myVec.begin() + Y + 1;
vector<T> newVec(first, last);

This operation is performed at O(N) complexity.

Alternative STL Data Types

If efficiency is paramount and O(N) performance is unacceptable, other STL data structures can be considered:

• std::deque: A double-ended queue that provides efficient insertion and deletion at both ends. However, accessing elements at arbitrary positions within a deque is less efficient than with a vector.
• std::list: A doubly linked list that supports efficient insertion and deletion at any position. While it allows for arbitrary element access, it has a higher memory overhead compared to a vector.

The choice between a vector, deque, or list ultimately depends on the specific performance requirements and access patterns of your application.

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