public member function
<set>

std::multiset::erase

(1)
     void erase (iterator position);
(2)
size_type erase (const value_type& val);
(3)
     void erase (iterator first, iterator last);
(1)
iterator  erase (const_iterator position);
(2)
size_type erase (const value_type& val);
(3)
iterator  erase (const_iterator first, const_iterator last);
Erase elements
Removes elements from the multiset container.

This effectively reduces the container size by the number of elements removed, which are destroyed.

The parameters determine the elements removed:

Parameters

position
Iterator pointing to a single element to be removed from the multiset.
Member types iterator and const_iterator are bidirectional iterator types that point to elements.
val
Value to be removed from the multiset. All elements with a value equivalent to this are removed from the container.
Member type value_type is the type of the elements in the container, defined in multiset as an alias of its first template parameter (T).
first, last
Iterators specifying a range within the multiset container to be removed: [first,last). i.e., the range includes all the elements between first and last, including the element pointed by first but not the one pointed by last.
Member types iterator and const_iterator are bidirectional iterator types that point to elements.

Return value

For the value-based version (2), the function returns the number of elements erased.

Member type size_type is an unsigned integral type.

The other versions return no value.
The other versions return an iterator to the element that follows the last element removed (or multiset::end, if the last element was removed).

Member type iterator is a bidirectional iterator type that points to elements.

Example

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// erasing from multiset
#include <iostream>
#include <set>

int main ()
{
  std::multiset<int> mymultiset;
  std::multiset<int>::iterator it;

  // insert some values:
  mymultiset.insert (40);                            // 40
  for (int i=1; i<7; i++) mymultiset.insert(i*10);   // 10 20 30 40 40 50 60

  it=mymultiset.begin();
  it++;                                              //    ^

  mymultiset.erase (it);                             // 10 30 40 40 50 60

  mymultiset.erase (40);                             // 10 30 50 60

  it=mymultiset.find (50);
  mymultiset.erase ( it, mymultiset.end() );         // 10 30

  std::cout << "mymultiset contains:";
  for (it=mymultiset.begin(); it!=mymultiset.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

Output:
mymultiset contains: 10 30

Complexity

For the first version (erase(position)), amortized constant.
For the second version (erase(val)), logarithmic in container size, plus linear in the number of elements removed.
For the last version (erase(first,last)), linear in the distance between first and last.

Iterator validity

Iterators, pointers and references referring to elements removed by the function are invalidated.
All other iterators, pointers and references keep their validity.

Data races

The container is modified.
The elements removed are modified. Concurrently accessing other elements is safe, although iterating ranges in the container is not.

Exception safety

Unless the container's comparison object throws, this function never throws exceptions (no-throw guarantee).
Otherwise, if a single element is to be removed, there are no changes in the container in case of exception (strong guarantee).
Otherwise, the container is guaranteed to end in a valid state (basic guarantee).
If an invalid position or range is specified, it causes undefined behavior.

See also

multiset::clear
Clear content (public member function )
multiset::insert
Insert element (public member function )
multiset::find
Get iterator to element (public member function )

C++