hash_map unordered_map map之间的比较

最新推荐文章于 2025-04-24 21:19:46 发布

转载最新推荐文章于 2025-04-24 21:19:46 发布 · 241 阅读

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本文介绍了C++标准库中unordered_map的引入背景及其与早期非标准实现如hash_map的区别。随着C++11的发布，一种新的哈希表实现被加入到标准库中，并命名为unordered_map以避免与现有非标准实现冲突。

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map与unordered_map的区别

见http://blog.youkuaiyun.com/orzlzro/article/details/7099231

hash_map与unordered_map的区别

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.

Starting with C++11 a hash table implementation has been added to the C++ standard library. 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_table in their code.

The chosen alternate name is unordered_map which really is more descriptive as it hints at the class's map interface and the unordered nature of its elements.