Does an iterator iterate through boost::unordered_set or boost::unordered_map in the same order as long as the set's unchanged?
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05-07-2021 - |
Вопрос
Does an iterator iterate through boost::unordered_set
or boost::unordered_map
in the same order as long as the set or the map is unchanged?
Решение
Some implementations of a hash map will reorder the items that hash to the same bin, putting the most recently accessed item at the front of a list, as an optimization. This would change the order. I'm not aware that boost::unordered_map
does this, but in the future you might end up substituting std::unordered_map
and it will all depend on your compiler's implementation.
Другие советы
It should be deterministic but as long as they are so-called unordered, you should not rely on this to iterate over your elements.
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