Creating a new C++ subvector?

Question

Say I have a vector with values [1,2,3,4,5,6,7,8,9,10]. I want to create a new vector that refers to, for example, [5,6,7,8]. I imagine this is just a matter of creating a vector with pointers or do I have to push_back all the intermediary values I need?

Answer 1

One of std::vector's constructor accepts a range:

std::vector<int> v;  // Populate v. for (int i = 1; i <= 10; i++) v.push_back(i);     // Construct v1 from subrange in v. std::vector<int> v1(v.begin() + 4, v.end() - 2); 

Answer 2

This is fairly easy to do with std::valarray instead of a vector:

#include <valarray> #include <iostream> #include <iterator> #include <algorithm>  int main() {   const std::valarray<int> arr={0,1,2,3,4,5,6,7,8,9,10};    const std::valarray<int>& slice = arr[std::slice(5, // start pos                                                    4, // size                                                    1  // stride                                                   )];  } 

Which takes a "slice" of the valarray, more generically than a vector.

For a vector you can do it with the constructor that takes two iterators though:

const std::vector<int> arr={0,1,2,3,4,5,6,7,8,9,10}; std::vector<int> slice(arr.begin()+5, arr.begin()+9);