how to remove all even integers from set in c++

Question

I\'m new to C++. I\'d like to know how experienced coders do this.

what I have:

set s;
s.insert(1);
s.insert(2);
s.insert(3);
s.insert(4);         


        

Answer 1

The best way is to use the combination of remove_if and erase

s.erase(remove_if(s.begin(), s.end(), evenOddFunctor), s.end())

This will be helpful http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Erase-Remove

Also Refer to effective STL by scott meyers

Edit: Although my solution is wrong i am not deleting it. It might be a good learning for someone like me who does not about mutable/immutable iterators

Answer 2

You don't need to go back to the start. set::erase only invalidates iterators that refer to the item being erased, so you just need to copy the iterator and increment before erasing:

for(set<int>::iterator itr = s.begin(); itr != s.end();)
{
    set<int>::iterator here = itr++;
    if (!(*here % 2))
        s.erase(here);
}

Answer 3

 for(set<int>::iterator itr = s.begin(); itr != s.end(); ){
  if (!(*itr % 2))
      s.erase(itr++);

  else ++itr;
 }

effective STL by Scott Myers

Answer 4

Erasing an element from std::set only invalidates iterators pointing to that element.

Get an iterator to the next element before erasing the target element.