std:: erase_if (std::flat_multiset)

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 . Otherwise, the behavior is undefined.

Parameters

Return value

The number of erased elements.

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.

Example

#include <iostream>
#include <flat_set>
 
void println(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};
    println("Original:\n", data);
 
    auto divisible_by_3 = [](auto const& x) { return (x % 3) == 0; };
 
    const auto count = std::erase_if(data, divisible_by_3);
 
    println("Erase all items divisible by 3:\n", data);
    std::cout << count << " items erased.\n";
}

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.

See also