std::experimental::erase_if (std::unordered_set)

From cppreference.com

Defined in header <experimental/unordered_set>
template< class Key, class Hash, class KeyEqual, class Alloc, class Pred >
void erase_if( std::unordered_set<Key, Hash, KeyEqual, Alloc>& c, Pred pred );
(library fundamentals TS v2)

Erases all elements that satisfy the predicate pred from the container. Equivalent to

for (auto i = c.begin(), last = c.end(); i != last;)
{
    if (pred(*i))
        i = c.erase(i);
    else
        ++i;
}

Parameters

c - container from which to erase
pred - predicate that determines which elements should be erased

Complexity

Linear.

Example

#include <experimental/unordered_set>
#include <iostream>
 
template<typename Os, typename Container>
inline Os& operator<<(Os& os, Container const& container)
{
    os << "{ ";
    for (const auto& item : container)
        os << item << ' ';
    return os << "}";
}
 
int main()
{
    std::unordered_set<int> data{3, 3, 4, 5, 5, 6, 6, 7, 2, 1, 0};
    std::cout << "Original:\n" << data << '\n';
    auto divisible_by_3 = [](auto const& x) { return (x % 3) == 0; };
    std::experimental::erase_if(data, divisible_by_3);
    std::cout << "Erase all items divisible by 3:\n" << data << '\n';
}

Possible output:

Original:
{ 0 1 2 7 6 5 4 3 }
Erase all items divisible by 3:
{ 1 2 7 5 4 }

See also

removes elements satisfying specific criteria
(function template)