std::vectors 的 std::vectors 连续性 [英] std::vector of std::vectors contiguity

问题描述

我知道 std::vector 在内部连续地存储它的数据(除非它是 std::vector)，都在旧的 中>C++03 标准和新的C++11.

I know that std::vector<T> internally stores it's data contiguously (unless it is std::vector<bool>) both in the old C++03 standard and the new C++11.

处理这个问题并引用标准的不错的 stackoverflow 问题:answer、答案.

Nice stackoverflow questions that deal with this and quote the standard: answer, answer.

嵌套向量中的数据怎么样 std::vector ;>?它是如何存储的?

What about the data inside nested vectors std::vector <std::vector <T> >? How is that stored?

如果每个内部向量都需要连续存储它的数据，那么 &v[n] == &v[0] + n for all 0 <= n .

If every internal vector needs to store it's data contiguously, how can it be true that &v[n] == &v[0] + n for all 0 <= n < v.size().

用稍微不同的话说，是否可以简单地"并顺序地(通过指针或类似物)访问存储在这种嵌套结构中的所有元素一维向量?

To phrase this slightly different, is it possible to access all the elements stored in such nested structure "simply" and sequentially (via a pointer or similar) the same way it can be done for a 1-D vector?

推荐答案

没有.vector 的元素存储在动态分配的内存块中；否则，vector 的容量无法增加.vector 对象只包含一个指向该块的指针.

No. The elements of a vector are stored in a dynamically allocated block of memory; otherwise, the capacity of the vector could not increase. The vector object just holds a pointer to that block.

元素顺序存储的要求仅适用于元素本身，而不适用于这些元素的任何动态分配的成员.

The requirement that the elements be stored sequentially applies only to the elements themselves, and not to any dynamically allocated members of those elements.

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