vector<vector<int> > vec( n , vector<int> (m, 0));
auto M = 4; // num of rows auto N = 3; // num of cols in each row auto default_value = 1; // default value of all int elements std::vector<std::vector<int>> matrix(M, std::vector<int>(N, default_value));
// Initializing 2D vector "vect" with // values vector<vector<int> > vect{ { 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 } };