filling a vector of vector

[gumus]

Hi,
It may be a simple question. But, how can i fill a vector of vector in a loop? Below is what I have tried:

std::vector< std::vector<flo at> > vec;
for (int i=0; i<n++; i++){
for (int j=0; j<m; j++){
//I tried the below ones. But none works.
vec[i][j]=i*j;
vec.push_back(i *j);
vec[i].push_back(i*j) ;
vec[i][j].push_back(i*j) ;
}

Thanks.

[D_C]

vec expects you to pass a vector, you are passing it an integer. Define a new vector

std::vector<float> vec_flt;
for(){
       for() {
                vec_flt.push_back((float)(i*j));
              }
     }
// Now you can push vec_flt into vec
vec.push_back(vec_flt);

I must admit, I don't know why you see it necessary to use a vector of vectors.

[pra1983]

usage of vectors?

can u tell me then how to printout the data.... from the same thing vec...

and how to traverse through the vec then....

how to pick an element or check an intermediate element from the vec.....

[Ganon11]

Once you build your vector of vectors, you can treat it like a 2D array when traversing and printing.

[pra1983]

Once you build your vector of vectors, you can treat it like a 2D array when traversing and printing.

actially i am trying to fill the vector with the data from a file. Can u suggest me how to fill the vector.(Is it the same way how i fill the 2D matrix).Can i use a single element of the vector from the middle of the vector at a time.Please let me know how to do that......