Question

I want to give the dimensions of the vector after declaring it through some other function.

This is because i will come to know the dimensions of vector afterwards.

Is there any way i can do that without using loops.

e.g

std::vector<std::vector<int>>my_vector;

........
........
........

and down in some other function i will declare the dimensions of it.

my_vector(2,5);

something like that….

Answer 1

my_vector = std::vector< std::vector<int> >(2, std::vector<int>(5));

or in C++11 as Xeo notes:

my_vector = {2, std::vector<int>(5)};

I think this approach is better than resize, because if you change the size several times, you might end up with a jagged matrix:

my_vector.resize(1, std::vector<int>(3));
my_vector.resize(2, std::vector<int>(5));

Now row one is 3 elements and row two is 5 elements.