Vector of Vectors to create matrix

Question

I'm attempting to get the dimensions of a 2D matrix as an input. Then utilize user input to fill in the blanks in this matrix. I attempted to accomplish this using vectors (vectors of vectors). However, anytime I try to read in data and append it to the matrix, I get problems.

//cin>>CC; cin>>RR; already done
vector<vector<int> > matrix;
for(int i = 0; i<RR; i++)
{
    for(int j = 0; j<CC; j++)
    {
    cout<<"Enter the number for Matrix 1";
         cin>>matrix[i][j];
    }
}

I get a subscript out of range error whenever I try to execute this. 

Do you have any suggestions?

Answer 1

Before accessing any elements, you must first set the vector of vectors to the right size. 

You may do it this way:

// assumes using std::vector for brevity
vector<vector<int>> matrix(RR, vector<int>(CC));

This generates a vector filled with RR size CC vectors.