Vector of Vectors to create matrix

Question

I am trying to take in an input for the dimensions of a 2D matrix. And then use user input to fill in this matrix. The way I tried doing this is via vectors (vectors of vectors). But I have encountered some errors whenever I try to read in data and append it to the matrix.

//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];     } } 

Whenever I try to do this, it gives me a subscript out of range error. Any advice?

Answer 1

You have to initialize the vector of vectors to the appropriate size before accessing any elements. You can do it like this:

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

This creates a vector of RR size CC vectors, filled with 0.