HOW TO PLAY SUDOKU (BRIEF RULES)
Sudoku is the new puzzle craze, originating from Japan. You are given a 9x9 grid which has been divided into nine 3x3 boxes. The aim of the game is very simple: to fill each row, column and 3x3 box with the numbers from 1 to 9 inclusive.
Although the puzzle looks like a giant magic square, in fact there is no mathematics involved. In a typical grid, approximately 30 of the numbers will be given to you. From thereon, you can deduce all the other digits using logic alone.
To begin, look at the digit which occurs most frequently in the grid. In which rows, columns and boxes is it missing? Also look at rows, columns and boxes which are almost complete — which numbers are missing and where could they go? The rest is up to you!
SUDOKU — A BEGINNER'S GUIDE
By David J. Bodycombe
Welcome to Sudoku, the new puzzle craze. A standard grid consists of 81 squares in a 9x9 arrangement (see Figure 1). You'll notice that the grid is split up into nine 3x3 boxes, and that some of the cells already contain digits. This particular grid is about average in difficultly, but don't worry — we'll guide you through it.
The aim of game is surprisingly simple: to fill each row, column and 3x3 box with the numbers from 1 to 9 inclusive. The best-devised puzzles allow you to complete the grid logically, without resorting to guesswork.
Let's take our first steps to the answer (see Figure 2). Remember that each row, column and box must contain every digit. You'll note that there is a "1" in the second and third columns. Therefore, there must be a "1" in the first column too, and the only 3x3 box it can go into is the bottom-left one. There's only one free space it can go (circled).
On that same diagram, we'll also look at some of the other "1"s. There isn't one in the sixth row, and — by drawing imaginary lines crossing out all those rows and columns that already contain a "1" — you can clearly see that there is only one place it can go in that middle-right box.
Let's do another example (figure 3). There isn't a "9" yet in the top-right 3x3 box. However, four of the five empty cells would lead to a contradiction, since those rows and columns already contain a "9". In fact, you can then go on to place nearly every other "9" using the same rule.
The situation is now shown in Figure 4. Let's take a look at that left-hand column, because it's nearly full. Only the numbers "5", "6" and "8" remain to be placed. However, look at the top row. That already contains a "6" and an "8", so the "5" must go there. From here, it's possible to fill in the rest of the column. This, in turn, allows you to deduce other squares.
Figure 5 shows us well on the way to cracking the puzzle. See if you can solve the rest of it yourself. Figure 6 shows the full solution. You may notice a pattern in the numbers. Most true Sudoku puzzles donŐt follow this pattern, so watch out.
There are more tricks to discover, but you're on your own for now. Just keep a look out for opportunities to deduce information, where you have lots of digits of the same type, or there are rows, columns and boxes that are nearly full. Enjoy your Sudoku-ing — and beware, it's addictive.
