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

std::vector< std::vector > is a vector of objects, that are stored in contiguous block of memory. The fact that these objects are vectors too is irrelevant though.

Although elements of the vector are stored in the contiguous block of memory, the memory where elements reside is not the part of the vector object itself.

"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?"
For accessing elements of std::vector, it's better to use operator[] or at() method than retrieving the address of first element and using pointer arithmetic. For multidimensional arrays represented as vector of vectors, I suggest you to stay with operator[], which is easy to use and easy to read as well: myVector[i][j]. Worth to see vector::at vs. vector::operator[] as well :)