how to make a 2d vector in c 2b 2b

1// Create a vector containing n 
2//vectors of size m, all u=initialized with 0
3vector<vector<int> > vec( n , vector<int> (m, 0));  

1vector< vector<int>> a(rows, vector<int> (cols));

1// Initializing 2D vector "vect" with 
2// values 
3vector<vector<int> > vect{ { 1, 2, 3 }, 
4                           { 4, 5, 6 }, 
5                           { 7, 8, 9 } }; 

12D vector