在C ++ STL中set和hashset之间有什么区别？ [英] What is the difference between set and hashset in C++ STL?

问题描述

我应该什么时候选择一个？
是否有任何建议使用正确的STL容器的指针？

When should I choose one over the other? Are there any pointers that you would recommend for using the right STL containers?

推荐答案

hash_set 是不是C ++标准的一部分的扩展。对于 set ，查找应该是O（1）而不是O（log n），因此在大多数情况下它会更快。

hash_set is an extension that is not part of the C++ standard. Lookups should be O(1) rather than O(log n) for set, so it will be faster in most circumstances.

当你遍历容器时，会看到另一个区别。 set 将以排序顺序传递内容，而 hash_set 将基本上是随机的（感谢Lou Franco）。

Another difference will be seen when you iterate through the containers. set will deliver the contents in sorted order, while hash_set will be essentially random (Thanks Lou Franco).

编辑：C ++ 11对C ++标准的更新引入了 unordered_set ，而不是 hash_set 。性能将类似，并由标准保证。名称中的无序强调迭代它将产生没有特定顺序的结果。

The C++11 update to the C++ standard introduced unordered_set which should be preferred instead of hash_set. The performance will be similar and is guaranteed by the standard. The "unordered" in the name stresses that iterating it will produce results in no particular order.

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