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std::erase_if (std::flat_multiset)

From cppreference.com
 
 
 
 
Defined in header <flat_set>
template< class Key, class Compare, class KeyContainer,

          class Pred >
std::flat_multiset<Key, Compare, KeyContainer>::size_type
    erase_if( std::flat_multiset<Key, Compare, KeyContainer>& c,

              Pred pred );
(since C++23)

Erases all elements that satisfy the predicate pred from c.

The predicate pred is satisfied if the expression bool(pred(std::as_const(e))) is true, where e is some element in c.

Key must be MoveAssignable.

Contents

[edit] Parameters

c - container adaptor from which to erase
pred - predicate that returns true if the element should be erased

[edit] Return value

The number of erased elements.

[edit] Complexity

Exactly c.size() applications of the predicate pred.

Exceptions

If erase_if throws, c remains in valid but unspecified (maybe empty) state.

Notes

The algorithm is stable, that is, the order of elements that are not deleted remains unchanged.

[edit] Example

#include <iostream>
#include <flat_set>
 
void print(auto rem, auto const& container)
{
    std::cout << rem << '{';
    for (char sep[]{0, ' ', 0}; const auto& item : container)
        std::cout << sep << item, *sep = ',';
    std::cout << "}\n";
}
 
int main()
{
    std::flat_multiset data{3, 3, 4, 5, 5, 6, 6, 7, 2, 1, 0};
    print("Original:\n", data);
 
    auto divisible_by_3 = [](auto const& x) { return (x % 3) == 0; };
 
    const auto count = std::erase_if(data, divisible_by_3);
 
    print("Erase all items divisible by 3:\n", data);
    std::cout << count << " items erased.\n";
}

Output:

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

[edit] See also

removes elements satisfying specific criteria
(function template) [edit]