How to delete an element from a vector while looping over it?

Question

I am looping through a vector with a loop such as for(int i = 0; i < vec.size(); i++). Within this loop, I check a condition on the element at that vector i

Answer 1

If you cannot use remove/erase (e.g. because you don't want to use lambdas or write a predicate), use the standard idiom for sequence container element removal:

for (auto it = v.cbegin(); it != v.cend() /* not hoisted */; /* no increment */)
{
    if (delete_condition)
    {
        it = v.erase(it);
    }
    else
    {
        ++it;
    }
}

If possible, though, prefer remove/erase:

#include 

v.erase(std::remove_if(v.begin(), v.end(),
                       [](T const & x) -> bool { /* decide */ }),
        v.end());