See the example below. Using only 1īs and 9īs, the 3x3 grid is filled so the 6 three-digit numbers so formed (in the 3 rows and 3 columns) are in the ascending order shown by the numbers around the grid:

      3   1   6
    +---+---+---+
  2 | 1 | 1 | 9 |
    +---+---+---+
  5 | 9 | 1 | 9 |
    +---+---+---+
  4 | 9 | 1 | 1 |
    +---+---+---+

That is, the 1st is in the 2nd column (111), the 2nd is in the 1st row (119), the 3rd is in the 1st column (199), and so on.

Do the same with these three 4x4 grids.

      3   7   6   4         3   2   8   5         2   4   5   6
    +---+---+---+---+     +---+---+---+---+     +---+---+---+---+
  5 |   |   |   |   |   1 |   |   |   |   |   1 |   |   |   |   |
    +---+---+---+---+     +---+---+---+---+     +---+---+---+---+
  2 |   |   |   |   |   7 |   |   |   |   |   7 |   |   |   |   |
    +---+---+---+---+     +---+---+---+---+     +---+---+---+---+
  8 |   |   |   |   |   6 |   |   |   |   |   3 |   |   |   |   |
    +---+---+---+---+     +---+---+---+---+     +---+---+---+---+
  1 |   |   |   |   |   4 |   |   |   |   |   8 |   |   |   |   |
    +---+---+---+---+     +---+---+---+---+     +---+---+---+---+

Posted by K Sengupta on 2023-05-21 02:39:12