提高:: unordered_map保持插入的顺序？ [英] boost::unordered_map maintains order of insertion?

问题描述

我要寻找它提供的std ::地图一样的界面，但仍保持在哪些元素插入的顺序的容器。既然不会在地图上太​​多的元素，查找性能是不是一个大问题。将提振::在这种情况下unordered_map 工作？即它保持插入的顺序。我是新来Boost库，因此想要知道究竟是什么意思通过'无序'？

I am looking for a container which provides std::map like interface but maintains the order in which elements are inserted. Since there will not be too many elements in the map, the lookup performance is not a big issue. Will boost::unordered_map work in this case? i.e. does it maintain the order of insertion. I am new to boost library and hence want to know what exactly meant by 'unordered' ?

推荐答案

unordered_map不保持插入的顺序。无序在这种情况下，意味着元素的观察到的顺序（当你一一列举，即）是不确定的，并且武断。事实上，我希望，在一个unordered_map元素的顺序可以在地图的生命周期中的变化，由于调整地图时老调重弹（这是依赖于实现虽然）

unordered_map doesn't maintain the order of insertion. Unordered in this case means that the observable order of elements (i.e. when you enumerate them) is unspecified and arbitrary. In fact, I would expect that the order of elements in an unordered_map can change during the lifetime of the map, due to rehashing when resizing the map (that's implementation dependent though)

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