C++

参考

<unordered_set>

unordered_multiset

public member function
<unordered_set>

std::unordered_multiset::erase

by position (1)
iterator erase ( const_iterator position );
by key (2)
size_type erase ( const key_type& k );
range (3)
iterator erase ( const_iterator first, const_iterator last );
Erase elements
Removes from the unordered_multiset container either the elements whose value is k or a range of elements ([first,last)).

This effectively reduces the container size by the number of elements removed, calling each element's destructor.

参数

position
Iterator pointing to a single element to be removed from the unordered_multiset.
成员类型const_iterator是一个 forward iterator 类型。
k
Value of the elements to be erased.
成员类型key_typeis the type of the elements in the container. In unordered_multiset containers it is the same asvalue_type相同，定义为类模板参数的别名（键).
first, last
Iterators specifying a range within the unordered_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.
Notice that unordered_multiset containers do not follow any particular order to organize its elements, therefore the effect of range deletions may not be easily predictable.
成员类型const_iterator是一个 forward iterator 类型。

返回值

Versions (1) and (3) return an iterator pointing to the position immediately following the last of the elements erased.
Version (2) returns the number of elements erased.

成员类型iterator是一个 forward iterator 类型。
成员类型size_type是一种无符号整型类型。

unordered_multiset 中的所有迭代器都对元素具有 const 访问权限：可以插入或移除元素，但在容器中不能修改它们。

示例

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// unordered_multiset::erase
#include <iostream>
#include <string>
#include <unordered_set>

int main ()
{
  std::unordered_multiset<std::string> myums =
  {"fish","duck","cow","cow","pig","hen","sheep"};

  myums.erase ( myums.begin() );                    // erasing by iterator
  myums.erase ( "sheep" );                          // erasing by key
  myums.erase ( myums.find("fish"), myums.end() );  // erasing by range

  std::cout << "myums contains:";
  for ( const std::string& x: myums ) std::cout << " " << x;
  std::cout << std::endl;

  return 0;
}
可能的输出
myums contains: pig cow cow


复杂度

Average case: Linear in the number of elements removed (which is constant for versions (1) and (2)).
Worst case: Linear in the container size.

迭代器有效性

Only the iterators and references to the elements removed are invalidated.
The rest are unaffected.
The relative order of iteration of equivalent elements not removed by the operation is preserved.
The relative order of iteration of the elements not removed by the operation is preserved.

另见

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