C++

参考

<map>

map

public member function
<map>

std::map::erase

(1)
     void erase (iterator position);
(2)
size_type erase (const key_type& k);
(3)
     void erase (iterator first, iterator last);
(1)
iterator  erase (const_iterator position);
(2)
size_type erase (const key_type& k);
(3)
iterator  erase (const_iterator first, const_iterator last);
Erase elements
Removes from the map container either a single element or a range of elements ([first,last)).

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

参数

position
Iterator pointing to a single element to be removed from the map.
This shall point to a valid and dereferenceable element.
成员类型iterator和const_iteratorare bidirectional iterator types that point to elements.
k
Key of the element to be removed from the map.
成员类型key_type是容器中元素的类型，在map中定义为其第一个模板参数（键).
first, last
Iterators specifying a range within the map 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 key-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 map::end, if the last element was removed).

成员类型iteratoris a bidirectional iterator type that points to an element.

示例

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// erasing from map
#include <iostream>
#include <map>

int main ()
{
  std::map<char,int> mymap;
  std::map<char,int>::iterator it;

  // insert some values:
  mymap['a']=10;
  mymap['b']=20;
  mymap['c']=30;
  mymap['d']=40;
  mymap['e']=50;
  mymap['f']=60;

  it=mymap.find('b');
  mymap.erase (it);                   // erasing by iterator

  mymap.erase ('c');                  // erasing by key

  it=mymap.find ('e');
  mymap.erase ( it, mymap.end() );    // erasing by range

  // show content:
  for (it=mymap.begin(); it!=mymap.end(); ++it)
    std::cout << it->first << " => " << it->second << '\n';

  return 0;
}
输出
a => 10
d => 40


复杂度

For the first version (erase(position)), amortized constant.
For the second version (erase(val)), logarithmic in container size.
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

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