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std::erase_if (std::set)

From cppreference.com
< cpp‎ | container‎ | set
Defined in header <set>
template< class Key, class Compare, class Alloc, class Pred >

typename std::set<Key,Compare,Alloc>::size_type

    erase_if(std::set<Key,Compare,Alloc>& c, Pred pred);
(since C++20)

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

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

Contents

[edit] Parameters

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

[edit] Complexity

Linear.

[edit] Example

#include <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::set 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; };
 
    const auto count = std::erase_if(data, divisible_by_3);
 
    std::cout << "Erase all items divisible by 3:\n" << data << '\n'
              << count << " items erased.\n";
}

Output:

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

[edit] See also

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