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从std::multimap<>中删除项目后,我可以继续使用迭代器吗?[副本]

multimap stl c++

2

Stéphane · 技术社区 · 17 年前

即使调用了multimap::erase(),我还能继续使用multimap迭代器吗?例如:

Blah::iterator iter;
for ( iter = mm.begin();
      iter != mm.end();
      iter ++ )
{
    if ( iter->second == something )
    {
        mm.erase( iter );
    }
}

这应该正常运行,还是迭代器在调用擦除后无效?参考网站,如 http://www.cplusplus.com/reference/stl/multimap/erase.html 对于迭代器的寿命,或者构造性/破坏性方法对迭代器的影响,他们出奇地沉默。

2 回复 | 直到 16 年前

1

17

Community Mohan Dere 8 年前

http://www.sgi.com/tech/stl/Multimap.html

Multimap has the important property that inserting a new element
into a multimap does not invalidate iterators that point to existing
elements. Erasing an element from a multimap also does not invalidate
any iterators, except, of course, for iterators that actually point to
the element that is being erased.

所以它应该看起来像这样:

Blah::iterator iter;
for ( iter = mm.begin();iter != mm.end();)
{
    if ( iter->second == something )
    {
        mm.erase( iter++ );
        // Use post increment. This increments the iterator but
        // returns a copy of the original iterator to be used by
        // the erase method
    }
    else
    {
        ++iter;   // Use Pre Increment for efficiency.
    }
}

另请参见: What happens if you call erase() on a map element while iterating from begin to end?

和

delete a specific entry in the map,but the iterator must point to the next element after the deletion

2

1

Igor Semenov 17 年前

C++标准23.1.2.8:

插入成员不得影响迭代器和对容器的引用的有效性,擦除成员应仅使迭代器和对已擦除元素的引用无效。

这是所有关联容器的共同要求,std::multimap就是其中之一。