从 std::multimap<> 中删除项目后，我可以继续使用迭代器吗？

发布于 2024-07-11 02:44:35 字数 498 浏览 5 评论 0 原文

即使在调用 multimap::erase() 之后，我还可以继续使用 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 );
    }
}

这是否应该正确运行，或者迭代器在调用擦除后是否失效？参考站点，例如 http://www.cplusplus.com/reference/stl/multimap /erase.html 对于迭代器的生命周期或迭代器的构造/破坏性方法的影响这个主题出奇地安静。

原文

Can I continue to use an multimap iterator even after a call to multimap::erase()? For example:

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

Should this be expected to run correctly, or is the iterator invalidated following the call to erase? Reference sites like http://www.cplusplus.com/reference/stl/multimap/erase.html are strangely quiet on this topic of the lifespans of iterators, or the effects of constructive/destructive methods on iterators.

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

风追烟花雨 2024-07-18 02:44:35

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.
    }
}

另请参阅：
如果在从开始到结束迭代时对地图元素调用擦除（）会发生

什么

？ -the-map-but-the-iterator-must-point-to-the-next-elemen#269717">删除映射中的特定条目，但迭代器必须指向删除后的下一个元素

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.

So it should look like this:

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.
    }
}

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

and

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

回复收藏 0 原文