C++ hash_map 和 unordered_map 的区别？
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Difference between hash_map and unordered_map?
提问by kidnamedlox
I recently discovered that the implementation of the hash map in C++ will be called unordered_map.
我最近发现在 C++ 中哈希映射的实现会被调用unordered_map。
When I looked up why they weren't just using hash_map, I discovered that apparently there are compatibility issues with the implementation of hash_mapthat unordered_mapresolves (more about it here).
当我抬起头，为什么他们不只是使用hash_map，我发现，显然有与实施的兼容性问题hash_map是unordered_map做出决议（更多关于它在这里）。
That wiki page doesn't give much more information so I wondering if anyone knew some of the issues with hash_mapthat unordered_mapresolves.
该 wiki 页面没有提供更多信息，所以我想知道是否有人知道hash_map该unordered_map解决方案的一些问题。
回答by Stef
Since there was no hash table defined in the C++ standard library, different implementors of the standard libraries would provide a non-standard hash table often named hash_map. Because these implementations were not written following a standard they all had subtle differences in functionality and performance guarantees.
由于 C++ 标准库中没有定义哈希表，标准库的不同实现者会提供一个非标准的哈希表，通常命名为hash_map. 因为这些实现不是按照标准编写的，所以它们在功能和性能保证上都有细微的差别。
Starting with C++11a hash table implementation has been added to the C++ standard library standard. It was decided to use an alternate name for the class to prevent collisions with these non-standard implementations and to prevent inadvertent use of the new class by developers who had hash_tablein their code.
从C++11开始，哈希表实现已添加到 C++ 标准库标准中。决定为该类使用一个替代名称，以防止与这些非标准实现发生冲突，并防止开发人员hash_table在其代码中无意中使用新类。
The chosen alternate name is unordered_mapwhich really is more descriptive as it hints at the class's map interface and the unordered nature of its elements.
所选择的替代名称unordered_map确实更具描述性，因为它暗示了类的地图界面及其元素的无序性质。
