C++

参考

<set>

multiset

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

参数

position
Iterator pointing to a single element to be removed from the multiset.
成员类型iterator和const_iteratorare 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.
成员类型value_typeis 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.
成员类型iterator和const_iteratorare bidirectional iterator types that point to elements.

返回值

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

成员类型size_type是一种无符号整型类型。

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).

成员类型iterator是指向元素的双向迭代器类型。

示例

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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;
}
输出
mymultiset contains: 10 30


复杂度

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.

迭代器有效性

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

数据竞争

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

异常安全

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.

另见

multiset::clear
清除内容 (公开成员函数)
multiset::insert
插入元素 (公开成员函数)
multiset::find
获取指向元素的迭代器 (公共成员函数)