[[1,1,1,1,1]]
push_back
[[1,1,1,1,1],[1,1,1,1,2]]
vector<vector<тип_который_нужен> > blah { {1, 2} };
blah.push_back({1, 4, 5});
std::vector<std::vector<int>> vector_of_vectors;
vector_of_vectors.push_back({ 1,1,1,1,1 });
std::cout << vector_of_vectors << std::endl; // [[1,1,1,1,1]]
vector_of_vectors.push_back({ 1,1,1,1,2 });
std::cout << vector_of_vectors << std::endl; // [[1,1,1,1,1],[1,1,1,1,2]]