std::vector of std::vectors contiguity

Question

I know that std::vector internally stores it\'s data contiguously (unless it is std::vector) both in the old C++03

Answer 1

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.

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