我注意到在有效的STL
向量是这样一种序列 默认情况下应该使用。
这是什么意思?似乎忽略效率向量可以做任何事情。
谁能给我一个场景，其中向量不是一个可行的选择，但必须使用列表?
当前回答
当你在序列中间有很多插入或删除时。例如，内存管理器。
其他回答
| std::vector | std::list |
|---|---|
| Contiguous memory. | Non-contiguous memory. |
| Pre-allocates space for future elements, so extra space required beyond what's necessary for the elements themselves. | No pre-allocated memory. The memory overhead for the list itself is constant. |
| Each element only requires the space for the element type itself (no extra pointers). | Each element requires extra space for the node which holds the element, including pointers to the next and previous elements in the list. |
| Can re-allocate memory for the entire vector any time that you add an element. | Never has to re-allocate memory for the whole list just because you add an element. |
| Insertions at the end are constant, amortized time, but insertions elsewhere are a costly O(n). | Insertions and erasures are cheap no matter where in the list they occur. |
| Erasures at the end of the vector are constant time, but for the rest it's O(n). | It's cheap to combine lists with splicing. |
| You can randomly access its elements. | You cannot randomly access elements, so getting at a particular element in the list can be expensive. |
| Iterators are invalidated if you add or remove elements to or from the vector. | Iterators remain valid even when you add or remove elements from the list. |
| You can easily get at the underlying array if you need an array of the elements. | If you need an array of the elements, you'll have to create a new one and add them all to it, since there is no underlying array. |
一般来说，当你不关心你使用的是哪种类型的顺序容器时，使用vector，但如果你在容器的任何地方做很多插入或擦除，而不是在末尾，你就会想要使用list。如果你需要随机访问，你就需要向量，而不是列表。除此之外，在某些情况下，根据应用程序需要其中一个或另一个，但一般来说，这些都是很好的指导原则。
保留迭代器的有效性是使用列表的原因之一。另一种情况是当你不希望在推送物品时重新分配向量。这可以通过巧妙地使用reserve()来管理，但在某些情况下，仅使用列表可能更容易或更可行。
当你在序列中间有很多插入或删除时。例如，内存管理器。
在表格中总结答案以供快速参考:
| Vector | List | |
|---|---|---|
| Access | Faster | Slower |
| Insert/Delete Operations | Slower | Faster |
| Memory Allocation | Contiguous | Non-contiguous |
| Size Pre-allocation | Need to be reserved | Not necessary to reserve |
| Space Required Per Element | Only for the element itself | For element and pointers to next (and optionally previous elements) |
基本上，vector是一个具有自动内存管理功能的数组。数据在内存中是连续的。试图在中间插入数据是一项代价高昂的操作。
在列表中，数据存储在不相关的内存位置。在中间插入数据并不需要复制一些数据来为新数据腾出空间。
为了更具体地回答你的问题，我将引用这一页
对于访问元素以及从序列末尾添加或删除元素，向量通常是最有效的。对于涉及在末尾以外的位置插入或删除元素的操作，它们的性能不如deques和list，并且迭代器和引用的一致性也不如list。
