std::erase_if (std::unordered_set)
From cppreference.com
< cpp | container | unordered set
| Defined in header <unordered_set>
|
||
| template< class Key, class Hash, class KeyEqual, class Alloc, class Pred > typename std::unordered_set<Key, Hash, KeyEqual, Alloc>::size_type |
(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();
Parameters
| c | - | container from which to erase |
| pred | - | predicate that returns true if the element should be erased |
Return value
The number of erased elements.
Complexity
Linear.
Example
Run this code
#include <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 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"; }
Possible output:
Original:
{ 0 1 2 7 6 5 4 3 }
Erase all items divisible by 3:
{ 1 2 7 5 4 }
3 items erased.See also
| removes elements satisfying specific criteria (function template) |