右下乘法表

Question

I'm writing a code to output the bottom right of a multiplication table...I can get the bottom left and the top right, but I get stuck trying to get the bottom right. I'm assuming that column needs to = 12, but whenever I try to input this, it gives me an error or the same answer as before. The output is supposed to look like the n's at the beginning of the code.

     n
    nn
   nnn

public static void main(String[] args) {
    //   // part 3: lower-triangular multiplication table
    for (int row=1; row<=12; row++) {
        for (int column=1; column <= row; column++)   
            System.out.printf("%5d", row*column);
        for (int column = row; column <= 0; column++)
        System.out.printf("%3c", ' ');
        System.out.println();

    }

Answer 1

To print the bottom (or top) right of a table, we need to iterate over the full table and omit entries

The entries omitted are replaced with whitespace so that the other entries that are printed will line up correctly

To determine if an entry is in a specific area, we can compare the X ( col ) and Y ( row ) values against the size ( size ) of the table

 1 2 ... X
1
2
...
Y

Top left includes (1,1), (1,Y), and (X,1), but not (X,Y) - X+Y < size+2 (+2 comes from 1 indexed vs 0 indexed)

Bottom left includes (1,1), (1,Y), and (X,Y), but not (X,1) - X <= Y

Top right includes (1,1), (1,Y), and (X,1), but not (X,Y) - X >= Y

Bottom right includes (1,Y), (X,1), (X,Y), but not (1,1) - size-X < Y

Code:

int size = 12; //size of the multiplication table
for(int row = 1; row <= size; row++) //go row by row
{
    for(int col = 1; col <= size; col++) //go column by column
        if(size - col < row) //in the bottom right area
            System.out.printf("%5d", row * col); //print the number
        else
            System.out.print("     "); //print whitespace for formatting
    System.out.println(); //end of the row, go to the next line
}

Outputs:

Size=4

               4
          6    8
     6    9   12
4    8   12   16

Size=12

                                                       12
                                                  22   24
                                             30   33   36
                                        36   40   44   48
                                   40   45   50   55   60
                              42   48   54   60   66   72
                         42   49   56   63   70   77   84
                    40   48   56   64   72   80   88   96
               36   45   54   63   72   81   90   99  108
          30   40   50   60   70   80   90  100  110  120
     22   33   44   55   66   77   88   99  110  121  132
12   24   36   48   60   72   84   96  108  120  132  144