Question

Say I have a vector / list whatever of ints populated with 2300 values
I want to be able to easily slice this into 4 vectors /lists (not necessarily of equal size).
e.g.

vec1 ( elements 0 - 500 )
vec2 ( elements 501 - 999)
vec3 ( elements 1001 - 1499)

etc.

Answer 1

A common way to do it would be to use the one container, and just define separate iterator ranges over it.

std::vector<int> vec(2300);

it0 = vec.begin();
it1 = vec.begin() + 500;
it2 = vec.begin() + 1000;
it3 = vec.begin() + 1500;
it4 = vec.begin() + 2000;
it5 = vec.end();

Now, the first range is simply defined by the iterators it0 and it1. The second by it1 and it2, and so on.

So, if you want to apply a function to every element in the third range, you’d simply do this:

std::for_each(it2, it3, somefunc);

Actually copying the elements into separate containers may be unnecessary, and would carry a performance cost.