对于 std::set 的 std::inserter 使用 .begin() 与 .end() 之间有区别吗？
it1和it2有什么区别吗？
std::set<sometype> s;
auto it1 = std::inserter(s, s.begin());
auto it2 = std::inserter(s, s.end());
If there is any difference between it1 and it2?
std::set<sometype> s;
auto it1 = std::inserter(s, s.begin());
auto it2 = std::inserter(s, s.end());
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。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱，如果其他用户或者作者回复了您的评论，将不能在第一时间通知您！
发布评论
评论（2）
实际上，并不多。如果您将大量已排序的元素插入到空的
set中，则第二个会稍快一些，但仅此而已。std::insert_iterator使用迭代器调用insert；std::set将其解释为提示，如果插入紧接在提示之前，则以恒定时间（而不是 lg n）插入。 （实际上，如果set为空，我认为两者都会做完全相同的事情。）In practice, not much. If you're inserting a large number of already in order elements into an empty
set, the second will be somewhat faster, but that's about it.std::insert_iteratorcallsinsertwith the iterator;std::setinterprets it as a hint, and inserts in constant time (rather than lg n) if the insertion is immediately before the hint. (Actually, if thesetis empty, I think both will do exactly the same thing.)来自 http://www.sgi.com/tech/stl/insert_iterator.html
然而，在有序关联容器的情况下，insert_iterator 构造函数中的迭代器几乎是无关紧要的。新元素不一定会形成连续的范围；它们将按键升序出现在容器中的适当位置。它们的插入顺序仅影响效率：将已排序的范围插入排序关联容器是一个 O(N) 操作。
From http://www.sgi.com/tech/stl/insert_iterator.html
In the case of a Sorted Associative Container, however, the iterator in the insert_iterator's constructor is almost irrelevant. The new elements will not necessarily form a contiguous range; they will appear in the appropriate location in the container, in ascending order by key. The order in which they are inserted only affects efficiency: inserting an already-sorted range into a Sorted Associative Container is an O(N) operation.