2D Vector - push_back, erase

[luckycusp]

std::vector< std::vector<double> > my_vector;

I have this 2D vector. How can I insert a double element to position(0,0) i.e how can I push_back such that my_vector[0][0] contains a double value. Subsequently, how could I add a double element to position my_vector[1][0]. Any other solution other than this:-

std::vector<double> tmp_vector;
my_vector.push_back(tmp_vector);
/* for my_vector[0][0] */
my_vector[0].push_back(2.5);
/* for my_vector[1][0] */
my_vector.push_back(tmp_vector);
my_vector[1].push_back(3.5);

How can I delete an element from a 2D vector? for example I want to remove element my_vector[2][3]. Could I use the erase function? Please help how to use erase function.

ps: I know it would be a very inefficient way of executing a program but I dont really care about time-optimization. Important for me is to finish the job somehow!

[firedraco]

You would call .erase() on the second vector, on the third element.

e.g. to delete [4][4]:

my_vector[4].erase(my_vector.begin()+3);

[luckycusp]

firedraco

If I want to delete a row say 3rd row, would this work??

my_vector.erase(my_vector.begin()+2);

or can I not use just this? I dont think I would ever need to use begin() as it always will be zero..

my_vector.erase(2);

Or am I missing some point?

[luckycusp]

Also another question, how can I pass a vector to a function, such that changes in the vector can be seen in the main function (pass by reference, pass by pointers)?

Ex:-

void My_Func(int **my_array)
{
my_array[0][0] = 5;
}
int main()
{
int a[5][10];
cout<<a[0][0];
My_Func(a);
cout<<a[0][0];
}

output:-
0
5

Now I would like a function:-

void My_Func(vector< vector<int> > my_vector)
{
 my_vector[0][0] = 5;
}
int main()
{
vector< vector<int> > a(5,10);
cout<<a[0][0];
My_Func(a);
cout<<a[0][0];
}

output:-
0 (not sure!)
5

ps: I wouldnt implement the my_func in this manner(as it could access illegal addresses if I for example use a[100][100]), but its just to make the question more clear.

[jsmith]

vector.begin() does not return 0. It returns an iterator to the first element in the vector whose index is zero.
So yes, you need begin() + 2.

void My_Func( vector<vector<int> >& my_vector )
{
}