c++ - How get next (previous) element in std::list without incrementing (decrementing) iterator?

Question

Say I have an std::list<int> lst and some std::list<int>::iterator it for iterating through the list. And depended to value of the it I want to use it + 1 or it - 1 in my code. Is there some good way to do that like next(), prev() (I couldn't find such things in stl documentation)? Or should I copy the it each time and increment(decrement) the copy?

Answer 1

Yes, since C++11 there are the two methods you are looking for called std::prev and std::next. You can find them in the iterator library.

Example from cppreference.com

#include <iostream>
#include <iterator>
#include <vector>

int main() 
{
    std::list<int> v{ 3, 1, 4 };

    auto it = v.begin();

    auto nx = std::next(it, 2);

    std::cout << *it << ' ' << *nx << '
';
}

Output:

3 4