Unable to add the columns and rows of a 2D array

Question

I am currently having some difficulty adding the total columns in a data file I was given, shown below:

   46.70   83.20   39.40   18.00   42.40   63.60
   29.10   12.40    9.50   74.80   43.40   55.70
   13.90   96.70   11.70   71.20   39.90   46.20
   22.50   84.30   76.00   27.40   50.60    7.10
   52.90   56.40   17.60   62.60   59.50   10.30
   46.00   67.90   47.00   58.70   75.20   64.30
   25.70   19.70   90.10   65.50   67.90   76.00
   11.10   97.70   64.10   75.00   65.20   38.80
   96.30   48.60   19.20   48.40   69.70   66.60
   17.50   74.10   46.10   23.00    6.10    5.40
   88.20   43.90   94.90   17.00   47.30   23.20
   35.00   40.60   86.10   11.80   18.20   74.60
   58.30   14.40   88.10   87.60   62.90   90.50
   68.90   82.40   65.30   55.50   63.30   97.80
   76.80   87.80   33.30   40.70   81.10   60.10
   80.40   84.70   16.40   24.20   93.30   27.70
   49.70   61.90   10.40   73.50   57.40   36.80
   82.70    9.50   20.20   69.10   39.60    5.50
   10.60   23.30   31.60   70.70   15.20   20.70
   64.20   95.80   42.80   40.20   64.80   10.70
   14.60   71.50   62.80   26.80   81.60   25.10
   95.20   61.80   20.60   36.20   86.60   26.20
   90.30   93.40    2.20   28.30   74.00   93.80
   10.40   27.50   53.70   17.90   60.70   23.80
   52.80   93.40   53.70   63.90   33.70   59.30
   60.50   62.20   41.00    9.70   18.40   50.10
   76.90   31.00   62.60   14.10   18.80   87.50
   27.30   71.60   46.90   28.30   39.50   13.00
   82.70   27.40   63.90   53.30   12.60   81.20
   30.30   74.90   44.50   40.50   23.10   82.20
   38.30   65.70   57.20   71.00   25.80   84.80
   22.30   75.30   27.20   15.30   40.20   20.70
   80.40   38.90   89.20   72.40   55.30   70.20
   95.60    5.00   75.40   96.50    8.40   72.70
   25.70    8.40   90.60   40.20   43.90   61.10
   11.50   65.90   55.00   20.80   48.60   84.70
   86.60   13.50   79.20   26.60   95.60   92.80
   10.50   84.10   30.00   61.30   37.60   63.40
   39.50   62.70   13.90   62.90   23.10   81.40
   27.00   67.50   94.20   55.20   49.40   34.30
    8.10   25.10   74.60   89.20   54.60   35.60
   97.00   95.30   77.10   12.40    8.60   63.10
   11.50   16.50   70.70    5.70   38.20   40.40
   45.50   73.40   55.20   74.50   95.10   14.80
   71.90   49.70   84.30   92.10   52.40   24.90
   21.20   46.00   63.70   88.90    5.40   10.70
   71.00   64.60   84.00   98.00   43.50    1.40
   46.70   32.60   24.40   36.50   10.60   14.60
   18.60   67.40   92.00   62.40   36.10   71.30
   39.60   74.10   89.60   15.00   73.30   89.30

I've currently been able to add the individual rows, attaining the proper maximum value of the sum of the rows (and the index where it occurs). However, I've been unable to add the correct number of columns (it somehow counts to 50 columns when there are only 6, and isn't adding the values of each column, instead it adds some values I have no idea where they came from). Here's my current code:

    const int NUM_ROWS = 50;
    const int NUM_COLS = 6;
    double scores[NUM_ROWS][NUM_COLS];
    double sumRows = 0, sumColumns = 0;
    int colIndex, rowIndex;
    double highestRow = 0, highestCol = 0;

    fstream fin("scores.txt");

    while (! fin.eof())
    {
        for (int i = 0; i < NUM_ROWS; i++)
        {
            for (int j = 0; j < NUM_COLS; j++)
            {
                fin >> scores[i][j];
            }
        }
    }

    fin.close();

    for(int i = 0; i < NUM_ROWS; i++)
    {
        for(int j = 0; j < NUM_COLS; j++)
        {
            sumColumns += scores[j][i];
        }

        cout << "The sum of " << i+1 << " Column is " << sumColumns << endl;

        if (sumColumns > highestCol)
        {
            highestCol = sumColumns;
            colIndex = i+1;
        }

        sumColumns = 0;
    }

    cout << endl;

    for(int i = 0; i < NUM_ROWS; i++)
    {
        for(int j = 0; j < NUM_COLS; j++)
        {
            sumRows += scores[i][j];
        }

        cout << "The sum of " << i+1 << " Row is " << sumRows << endl;

        if (sumRows > highestRow)
        {
            highestRow = sumRows;
            rowIndex = i+1;
        }

        sumRows = 0;
    }

    cout << "The total of the column with the highest total is: " << highestCol << " and occurs at Column #" << colIndex << endl;
    cout << "The total of the row with the highest total is: " << highestRow << " and occurs at Row #" << rowIndex << endl;

Thanks in advance!

Try changing `for(int i = 0; i < NUM_ROWS; i++) { for(int j = 0; j < NUM_COLS; j++) {` for the column sum to `for(int j = 0; j < NUM_COLS; j++) { for(int i = 0; i < NUM_ROWS; i++) { `. — Emmanuel Mathi-Amorim, Nov 16 '16 at 19:28
You might also want to look at [Why is iostream::eof inside a loop condition considered wrong?](http://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong) — Bo Persson, Nov 16 '16 at 19:37

score 0 · Accepted Answer · answered Nov 16 '16 at 19:34

The problem is here:

for(int i = 0; i < NUM_ROWS; i++)
{
    for(int j = 0; j < NUM_COLS; j++)
    {
        sumColumns += scores[j][i];
    }

    cout << "The sum of " << i+1 << " Column is " << sumColumns << endl;

    if (sumColumns > highestCol)
    {
        highestCol = sumColumns;
        colIndex = i+1;
    }

    sumColumns = 0;
}

As you can see you iterate through the rows in the outer loop and through the columns in the inner, but the sumColumns isn't adding the correct values.

Replace this:

 for(int i = 0; i < NUM_ROWS; i++)
 {
    for(int j = 0; j < NUM_COLS; j++)
    {
        sumColumns += scores[j][i];
    }

with this:

for(int j = 0; j < NUM_COLS; j++)
{
    for(int i = 0; i < NUM_ROWS; i++)
    {
        sumColumns += scores[i][j];
    }

Oh that makes perfect sense. I neglected to realize the importance of searching through the columns first. Thanks so much :)! — Reclaim, Nov 16 '16 at 19:37

score 0 · Answer 2 · answered Nov 16 '16 at 19:41

You're simply mixing up the loop variables.

for(int i = 0; i < NUM_COLS; i++)
    {
        for(int j = 0; j < NUM_ROWS; j++)
        {
            sumColumns += scores[j][i];
        }

        cout << "The sum of " << i+1 << " Column is " << sumColumns << endl;

        if (sumColumns > highestCol)
        {
            highestCol = sumColumns;
            colIndex = i+1;
        }

        sumColumns = 0;
    }

The first index of your 2D array is the ROW index, and you correctly used the inner loop variable (j) as the first index, so your outer loop iterates the columns, and your inner loop iterates through the rows of the current column, processing them. However, you mixed up the exit condition for the loops. If j is the row index, and i is the column index, then i should go from 0 to NUM_COLS and j should go from 0 to NUM_ROWS. Easy as that.

Unable to add the columns and rows of a 2D array

2 Answers2