How Can I Efficiently Extract Subvectors in C ?

Efficient Subvector Extraction from a Vector

In C , extracting a portion of a vector as a new vector can be performed using STL's vector class.

Construction Using Iterators

The most straightforward approach involves creating iterators to the desired range within the original vector and passing them as arguments to the constructor of the new vector. For instance:

vector<T>::const_iterator first = myVec.begin() + 100000;
vector<T>::const_iterator last = myVec.begin() + 101000;
vector<T> newVec(first, last);

This copies elements from index 100000 to 100999 into the new vector newVec, resulting in a vector of size 1000.

Limitations and Alternatives

However, this method is not the most efficient. Creating a new vector from a portion of an existing vector involves creating copies of the elements. If the vector is large, this can be time-consuming.

For performance-critical applications, alternative data structures like std::span or std::array can be considered. These offer more efficient ways to create views of subranges without requiring copies.

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