std::erase_if (std::unordered_set)

Since C++20

Header: <unordered_set>

Erases all elements that satisfy the predicate pred from c.

# Declarations

template< class Key, class Hash, class KeyEqual, class Alloc,
class Pred >
std::unordered_set<Key, Hash, KeyEqual, Alloc>::size_type
erase_if( std::unordered_set<Key, Hash, KeyEqual, Alloc>& c,
Pred pred );

(since C++20)

# Parameters

# Return value

The number of erased elements.

# Example

#include <iostream>
#include <unordered_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::unordered_set 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";
}

# See also