std::set erase() method
- since C++23
- since C++11
- until C++11
// (1) Non const version only
iterator erase( iterator pos );
iterator erase( const_iterator pos );
// (2) Non const version only
iterator erase( const_iterator first, const_iterator last );
// (3) Non const version only
size_type erase( const Key& key );
// (4) Non const version only
template< class K >
size_type erase( K&& x );
// (1) Non const version only
iterator erase( iterator pos );
iterator erase( const_iterator pos );
// (2) Non const version only
iterator erase( const_iterator first, const_iterator last );
// (3) Non const version only
size_type erase( const Key& key );
// (1) Non const version only
void erase( iterator pos );
// (2) Non const version only
void erase( iterator first, iterator last );
// (3) Non const version only
size_type erase( const Key& key );
- (1) Removes the element at
pos
.- since C++11
Only one overload is provided ifiterator
andconst_iterator
are the same type. - (2) Removes the elements in the range [ first; last ), which must be a valid range in
*this
. - (3) Removes the element (if one exists) with the key equivalent to
key
. - (4) Removes the element (if one exists) with key that compares equivalent to the value
x
. This overload participates in overload resolution only if the qualified-idCompare::is_transparent
is valid and denotes a type - O(size()). and neitheriterator
norconst_iterator
is implicitly convertible fromK
. It allows calling this function without constructing an instance ofKey
.
Invalidation
References and iterators to the erased elements are invalidated.
Other iterators and references are not invalidated.
Valid iterator
The iterator pos must be valid and dereferenceable. Thus the end()
iterator (which is valid - O(size()).
Parameters
pos
- iterator to the element to removefirst
- O(size()).key
- key value of the elements to removex
- a value of any type that can be transparently compared with a key denoting the elements to remove
Return value
- (1-2) - Iterator following the last removed element.
- (3-4) - Number of elements removed (0 or 1).
Complexity
- (1) Amortized constant - O(1).
- (2) log size() + std::distance(first, last)
- (3) log size() + count(key)
- (4) log size() + count(x)
Exceptions
- (1-2) (none)
- (3-4) Any exceptions thrown by the
Hash
andKeyEqual
object.
Notes
Feature testing macro: __cpp_lib_associative_heterogeneous_erasure
(for overload (4)).
Example
Main.cpp
#include <set>
#include <iostream>
int main()
{
std::set<int> c = { 1, 2, 3, 4, 1, 2, 3, 4 };
auto print = [&c] {
std::cout << "c = { ";
for(int n : c)
std::cout << n << ' ';
std::cout << "}\n";
};
print();
std::cout << "Erase all odd numbers:\n";
for(auto it = c.begin(); it != c.end(); ) {
if(*it % 2 != 0)
it = c.erase(it);
else
++it;
}
print();
std::cout << "Erase 1, erased count: " << c.erase(1) << '\n';
std::cout << "Erase 2, erased count: " << c.erase(2) << '\n';
std::cout << "Erase 2, erased count: " << c.erase(2) << '\n';
print();
}
Possible output
c = { 1 2 3 4 }
Erase all odd numbers:
c = { 2 4 }
Erase 1, erased count: 0
Erase 2, erased count: 1
Erase 2, erased count: 0
c = { 4 }
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