Sudoku - Day 2

The reason this puzzle is classified as a diabolical is because there are few givens. And the numbers that are solved via the givens do not lead you down any particular path to solve any other numbers, so we must drive directly into the logic.

Let's start with column 1 and see if we can fill any numbers in. I found nothing in row 1 to quantify even a guess. So let's look at column 2. The number 1, 4, 5, 7 and 8 cannot be solved, and 2, 3 and 9 are given, but let's look at the number 6. Available sqaures are A2, G2 and J2. Notice that D2, E2 and F2 cannot be 6 because F1 is the 6 for box 4 (In which row 2 is part of).

So the 6 cannot go in A2 because row A already has a 6 [A7] and cannot go in G2 because row G already has a 6 [G4]. So the only place the 6 can go is: J2. J2 = 6. COOL !

Now that we filled in that six, let's immediately look for the row rule in box set 3. (Rows G, H and J). The 6 can only go in the middle row (H) because [G6] and [J2] are already 6, and can only go in box 9 since there are already 6's in box 7 and box 8. That leaves [H7] and [H9]. Look at that poor 6 in [A7] that rules out Column 7 so the 6 has to go in [H9].

One last move before finishing for the day... Still focusing on Box Set 3 (Row G, H, J) Notice that lonely 8 in [H8]. And notice that 5 of 6 boxes are filled in Row J [J1 - J5]. Well, each row needs an 8 and since box 9 already has an 8 [H8], that eliminates J7, J8 and J9 from being 8, leaving only one choice, [J6].

So after three deep logic moves, our board now looks like this, and we are ready to move on.

Enjoy your weekend.

Dr. Sudoku.