C++迭代器有效性问题

Question

我正在从 http://www.cplusplus.com/reference/vector/vector/insert/ 学习 std::vector::insert 相关部分代码:

int main ()
{
  std::vector<int> myvector (3,100);
  std::vector<int>::iterator it;

  it = myvector.begin();
  it = myvector.insert ( it , 200 );

  myvector.insert (it,2,300);

  // "it" no longer valid, get a new one:
  it = myvector.begin();

为什么.insert操作后迭代器无效？

Answer 1

来自 this reference它说:

Causes reallocation if the new size() is greater than the old capacity(). If the new size() is greater than capacity(), all iterators and references are invalidated. Otherwise, only the iterators and references before the insertion point remain valid. The past-the-end iterator is also invalidated.