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 > |
(since C++20) | |
Erases all elements that satisfy the predicate pred from c.
Equivalent to
auto old_size = c.size(); for (auto first = c.begin(), last = c.end(); first != last;) { if (pred(*first)) first = c.erase(first); else ++first; } 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 <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"; }
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) | |
| (C++20)(C++20) |
removes elements satisfying specific criteria (niebloid) |