Saturday, February 11, 2006

Wanna Play?

Today is Saturday, and I'm in the mood for playing games.

One of the things I really enjoy is the UK Daily Telegraph's Sudoku puzzle. Fridays and Sundays, the puzzle is diabolical, and those are my favorites.

Go to where today's puzzle is waiting for you. I promise you; you don't need to do any math. It's a logic problem that you solve by the process of elimination.

The rules are simple: You have nine grids made up of nine spaces each. Every grid uses the numbers one through nine, but only once. In addition, you can only use the numbers one through nine ONCE in any row or any column.

I'll start you off on today's puzzle.

Print the puzzle and you'll see that the spaces have been identified, using horizontal numbers and vertical letters. So the "4" in the first space is in A-1 and A-3 contains a "7".

Look at the top three horizontal grids. You'll see that the number "5" is used by grid 2 in the second line (B-6) and by grid 3 in the third line (C-8). Since each number can ONLY be used once in any row or column, that means that the "5" will have to go in the first row in grid 1. Since spaces A-1 and A-3 are already filled, the "5" will have to go in A-2. See how easy it is?

I'll show you another example. Let's do the first three VERTICAL grids this time. Our old friend "7" is in A-3. Look at the grid below where the "7" is in E-2. Remember each row and column can only have any number one time. That means that in the bottom left hand grid, the "7" HAS to be in the first vertical row. Since G-1 and J-1 are filled, the "7" HAS to go in H-1.

Let's try a different strategy. Look at the column identified by the number 2. We now have six answers already filled in for that column. The only empty spaces are D-2, F-2 and J-2. If we look at the answers we already have in column 2, we know that we are missing the numbers "2", "6" and "9" because, of course, every column and every row must contain the numbers one through nine. We can't put the "2" in D-2 because row D already has a "2" in D-7. We can't put the "2" in J-2 because there's already a "2" in that row in J-9. So, by default, the "2" must go in F-2.

That leaves only the spaces D-2 and J-2 empty in row 2 and the numbers "6" and "9" needing homes. Again, by default, since J-5 has a "6", the "6" in our column 2 MUST go in D-2. That leaves the "9" to go in J-2.

One last boost for you: Let fill in ALL the numbers in the bottom left-hand grid. We already have six numbers filled in. All we need are a "1", "2" and "8." Remember our strategy for the first three grids? Look at the bottom middle grid where the "8" is in the second row (H-4). The "8" is in the last row for the bottom right grid (J-7). Of necessity, the "8" MUST go in the top row in the bottom left-hand grid (G-3). That leaves only the numbers "1" and "2" left to be filled in. They have to go in either H-3 or J-3. Since row J already has a "2" in J-9, we know that our "2" MUST go in "H-3. That leaves our "1" to go in J-3.

Easy, isn't it? Have fun. You have until 6 PM CST tomorrow night when the Daily Telegraph changes the puzzle again. If you finish before then, you can email your answers to the Daily Telegraph and they'll confirm whether you got it right. If you get stuck, email me and I'll try to help you out--if I can. I started the puzzle with you so I haven't finished it yet either, but hope to do so before I go to bed tonight.

Enjoy the rest of your weekend.

Warm regards,


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