/*push_back and pop_back are available in:

    std::vector
    std::deque
    std::list

They are not available in associative containers like
    std::set, 
    std::map, 
    std::unordered_set, and 
    std::unordered_map.
*/
#include <iostream>
#include <set>

int main() {
    std::set<int> s = {1,6,9,3,0};

    for(const auto &elem : s){
        std::cout<<elem<<' ';
    }
    std::cout<<std::endl;

    s.erase(9);
    for(const auto &elem : s){
        std::cout<<elem<<' ';
    }
}