clear() 是否影响 std::unordered_set 的桶数？
[英]Does clear() affect the bucket count of std::unordered_set?
问题描述
There are plenty of answers with std::vector , but what about std::unordered_set ? 
std::vector有很多答案，但是std::unordered_set呢？
My real question (closely related) is this;我真正的问题（密切相关）是这样的； is it efficient to reuse the same unordered set by clearing it before each use, if I reserve what I know to be a reasonable size beforehand?如果我事先保留了我知道的合理大小，通过在每次使用前清除它来重用相同的无序集是否有效？
1 个解决方案
解决方案1
6 已采纳 2014-09-05 00:05:12
Formal answer is: it depends on implementation.正式的答案是：这取决于实现。
Informal answer is: unordered_set inside has an array (of some kind) of buckets, and most likely the implementation is consistent with vector , so this array won't be deleted when clear() is called.非正式的回答是： unordered_set里面有一个（某种）bucket 的数组，并且很可能实现与vector一致，因此调用clear()时不会删除这个数组。 So calling clear() most likely will give some benefit.所以调用clear()很可能会带来一些好处。
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