Multidimensional array as input?

[mistersunnyd]

I have an assignment that asks the user to input two integer matrices and then multiplies them. The input format is:
1 2 3
4 5 6

so every space means one more column and every ENTER means one more row. Pressing ENTER after an empty line means the input is over. I am not quite sure how to implement this? Currently, I'm thinking of using while(getline(cin, str)) and checking if a char is ' ' or '\n'.

[Duthomhas]

Assuming you have a matrix class:

struct matrix
{
  vector <vector <int> > data;
  ...
};

You should implement a stream extraction operator (a function) to read one.

istream& operator >> ( istream& ins, matrix& m )
{
  ...
}

Then you can use the function to read the user's matrices:

  cout << "Enter the first matrix\n"
          "  (separate column values by spaces;\n"
          "   press enter for each row; press enter twice to finish):\n";
  matrix m1, m2;
  cin >> m1;
  cout << "Enter the second matrix:\n";
  cin >> m2;

So the issue now is to do this fancy input with spaces and enters.

Read each line as a string. Quit when EOF/fail or empty line.
Use a stringstream to split each line into values:

istream& operator >> ( istream& ins, matrix& m )
{
  string s;
  while (getline( ins, s ) and !s.empty())
  {
    m.emplace_back( vector <int> () );  // new row
    istringstream ss( s );
    int value;
    while (ss >> value)
    {
      m.back().emplace_back( value );  // add value to end of last row
    }
  }
  return ins;
}

You'll need to #include <ciso646> <iostream> <sstream> <string> and <vector>.

disclaimer: I typed this in off the top of my head, and I'm tired, so there may be an error in there.

Hope this helps.

[mistersunnyd]

Unfortunately, we must solve this problem with arrays.

[Duthomhas]

Okay, so:

struct matrix
{
  int data[MAX_ROWS][MAX_COLUMNS];
  int rows, columns;
  ...
};

istream& operator >> ( istream& ins, matrix& m )
{
  string s;
  int row = 0;
  while (getline( ins, s ) and !s.empty() and (row < MAX_ROWS))
  {
    istringstream ss( s );
    int value;
    int column = 0;
    while ((ss >> value) and (column < MAX_COLUMNS))
    {
      m.data[ row ][ column ] = value;
      columns++;
    }
    row++;
  }
  return ins;
}