array ,C++

RudraB · 07-12-2008, 04:03 PM

dear all, being a starter with C++, i am getting a problem with array.
i have a (say),NxN array in a file, from which i have to read the nXn
(n<N, obviously) chunk, and with each iteration, the size will
increase. the first problem of dynamic allocation is solved. but i am
getting a trouble that the code is reading first nxn element along row
and not the chunk. suppose i have a array:

Quote:

1 2 3 4 5 6
2 3 4 5 6 7
3 4 5 6 7 8
4 5 6 7 8 9
5 6 7 8 9 0

and if i write the code

Code:

int main() {

ifstream infile ;
infile.open("file", ios::in);

const unsigned row = 4 ;    // number of rows of the matrix, does not
match the row of file
const unsigned column = 3 ; // number of columns of the matrix;does
not match the column of file
//  float matrix[row][column] ;

  int Matrix[row][column-1] ;

  for(int ii = 0; ii < row; ++ii) {
    for(int jj = 0; jj < column; ++jj) {
        infile >> Matrix[ii][jj] ;
        cout << Matrix[ii][jj] << " " ;
    }
    cout << "\n" ;
  }

  return 0 ;

}

then we get the output:

Quote:

1 2 3
4 5 6
2 3 4
5 6 7

where i am intending it should give

Quote:

1 2 3
2 3 4
3 4 5
4 5 6

will you people plz help me?

traene · 07-12-2008, 04:08 PM

The istream operator>> reads always an int from your file. Since you don't check for new lines in your input you get the first output, not the supposed second. Try to store the size of your matrix in the file. something like:

Code:

6
5
1 2 3 4 5 6
 ...

RudraB · 07-12-2008, 04:14 PM

yes...and i have to put an endl...right? question is how!!!

traene · 07-12-2008, 04:26 PM

You can't do that with the operator>>. You can specify your file format:

cols
rows
.. here goes your matrix...

Or you can try reading the file line by line. Have a look for:
istream.getline(...)