c++ - vector 和指针

Question

vector 和指向其元素的指针的主要问题是，只要调用 push_back，它们就会在内存中重新分配，从而使指针无效。

我正在尝试实现后缀特里树，我将数据结构 node 存储在节点 vector 中。我知道对于大小为 n 的字符串，数字 n(n+1)/2 是 trie 中节点数的上限。

代码也是如此

std::string T = "Hello StackOverflow!";
std::vector<Node> nodes;

int n = T.length();
nodes.reserve(n*(n+1)/2);

保证我创建的任何指向 nodes 元素的指针都不会失效？也就是说，这会保证 vector 不会被重新分配吗？

---

编辑:我已经实现了这个，但在运行时我不断收到以下错误。

terminate called after throwing an instance of 'std::out_of_range'
what():  basic_string::at: __n (which is 0) >= this->size() (which is 0)
Aborted (core dumped)

知道是什么原因造成的吗？

Answer 1

根据标准(N4140):

23.3.6.3 vector capacity
....

void reserve(size_type n);

....
After reserve(), capacity() is greater or equal to the argument of reserve if reallocation happens; and equal to the previous value of capacity() otherwise. Reallocation happens at this point if and only if the current capacity is less than the argument of reserve().

和

23.3.6.5 vector modifiers
....

void push_back(const T& x);
void push_back(T&& x);

Remarks: Causes reallocation if the new size is greater than the old capacity. If no reallocation happens, all the iterators and references before the insertion point remain valid.