# Sudoku with only 8 predefined numbers

Have fun with my self-made Sudoku puzzle.

Solve this Sudoku puzzle using the standard Sudoku rules:
Fill any row, column and bold-framed area with the numbers 1 to 9.

Hint: It is not as difficult as it might look!

## Detailed explanation

Right at the beginning, we can tell that certain sets of cells must all contain the same number. Starting from the extreme bottom right cell, we can find a sequence of equal numbers (say this number is A) by considering each bold-framed area in turn starting from the bottom left and working to the right. This gives us a sequence of A's culminating in a 6, so A=6. Similarly, by starting from the B marked on the top row, we get a sequence of B's culminating in a 3, so B=3. This enables us to fill in all the 3's and 6's:

We can then find another sequence of equal numbers (say C) by starting from the extreme bottom left cell and considering each bold-framed area working up and to the right from there. This gives us a sequence of C's culminating in a 9, so C=9. We can also get a couple more 4's by considering where 4 can be in the second column and in the third bold-framed area from the left. This enables us to fill in all the 9's and 4's:

We can then use the same argument again to fill up the next diagonal and the next and the next:

Now the sixth row is almost full, so its leftmost cell must be 7; then there's only one possibility for where 7 can be in the fifth row, then in the fourth row, and so on. Once this diagonal of 7's is filled in, we can apply the same reasoning to get a diagonal of 5's, then a diagonal of 1's, then a diagonal of 2's: