In the next series of posts I will show you some Sudoku strategy tips to solve easy Sudoku puzzle. I’ll be using an easy puzzle as an example and working through it in this series of Sudoku tutorials. Including step by step instructions and pictures at each stage showing you how to solve this Sudoku puzzle. This is a great starting point if you would like to learn how to solve Sudoku but don’t know where to start, as it incorporates the main Sudoku principles/rules that I detailed in my previous post.
I wanted to go over the basics first before moving onto the advanced Sudoku tutorials, as the same basic Sudoku rules apply.
In this post I am just going to show you how to start a Sudoku puzzle, step by step. When a written step by step description for solving Sudoku can be quite long, which is why I am splitting this into a number of smaller posts. But, and this is my first tip, with practise you can learn how to not only be quicker at solving the puzzles but also progress to more difficult ones as you get better. Sudoku is a game of logic and elimination and with practise you will see how much fun they are to do as well as a good way to give your brain a bit of exercise!
Diagram 1 shows a blank 9×9 Sudoku grid. This is an easy Sudoku, Sudoku range from easy, medium, hard, difficult and advanced. Basically the more numbers pre-filled in a Sudoku puzzle the easier they should be to solve.
By applying the Sudoku rules a. each column, row and box must have all the numbers 1 to 9 in them and b. you can only have one occurrence of the numbers 1 to 9 in each column, row and box, you begin to solve your Sudoku.
Sudoku tip: As a good starting point, begin by scanning the whole grid for rows, columns and boxes that have the most numbers already pre-filled.
In diagram 2 you can see I have marked 2 columns A and B, these both have the most numbers in them, each having 6 pre-filled cells. Let’s see if that can help us in solving the puzzle?
Look at column A, remember it needs to have the numbers 1 to 9 in each column. And you can see that it already has pre-filled 3,9,5,2,6 and 7 thus this column is missing 1,4 and 8. Starting with the box that I have highlighted in yellow in diag.2 you can see that there is probably too many numbers missing in this box to try to use this to eliminate possibilities at this point. Similarly, the other 2 boxes underneath it, also have quite a few empty cells.
Let’s look at column B, we can see as it is already pre-filled with 7,4,6,2,5 and 1, it is missing the numbers: 3, 8 and 9.
Now before we continue, I want to put in my second of the Sudoku tips: Use a pencil to make notations in the grid, of possibles So you can rub it out once you know the answer definitely and also so you can keep track of what you have eliminated so far.
In diagram 3, you can see this tip in action.
If column B needs to be filled with 3, 8 and 9. Look at the first box (top right-hand corner), and you will notice there is already a 9 there, but not a 3 or 8. So the cell in the column B in this box, could be filled with either 3 or 8 and still adhere to the Sudoku rules. And so I put these possibilities in as temporary notation ‘3,8’, see diagram 3. Now you repeat this elimination and scanning process on the other boxes that contain the cells in column B. As it is the box underneath has all the column B cells pre-filled. But the bottom right-hand box has empty column B cells. We can see that this box already has an 8 in it so the 2 empty cells that are in column B must be for either 3 or 9, so I have put in the notation ‘3,9’ as possibilities, see diagram 4.
And so now column B has been scanned and the possibilities have been entered as notes. Obviously if you are doing it on paper do it in pencil and around the edges so you can rub it out and put in the actual answer once you know, in pen.
Sudoku Tips 3: For easy Sudoku, I usually only put in possible numbers when I have whittled it down to 2 possibilities, anymore and your grid can get quite cluttered up with notes. However for more difficult Sudoku you may find you have to note where you have more possibles in order to get anywhere with it!
Now we have looked at column B and noted the result of our eliminations, lets go back and see what this has uncovered. In the top right hand box, where we have noted ‘3,8’ you can see that there is already an ‘3’ in that row, so by elimination and adhering to the Sudoku rules, only an 8 can go in that cell, see diagram 5. Can I repeat this process to use the notations in the bottom right hand box? No there are still too many unknowns in this box.
However, I can now also continue to see if my notations in column B have opened possibles in the other box that contains it, ie the middle right hand box. This box is missing 1,3,4 and 9. Now we look at each of these numbers to see if they already occur in other columns and rows that make up this box. And you will see that the 1 could be put in any of the 4 empty cells (and not break the Sudoku rule of one occurrence per row, column and box). The number 3 could be in 3 of the 4 empty cells, it can’t go in the middle right cell because there is a 3 in that row already. Similarly, the 4 can only go in 3 of 4 cells, because the row for the bottom right corner of this box, has a 4 already in that row. And lastly, look at the number 9. However you can see it already occurs in 2 of the 3 columns of this box. So there is only one empty cell left that the 9 can be in without breaking the Sudoku rules. These 3 deductions have been included in diagram 6.
As you can see this is just a step by step how to start a Sudoku puzzle, and is already quite a long post, so I will stop at this point for now. But will continue with this step by step tutorial in my next post. What you will find is that with this method of scanning and eliminating you can continue with this puzzle and solve it yourself. With practise you will be able to solve Sudoku quickly and will become an expert at spotting the best place to start a Sudoku.
Once you have mastered the basics you will be able to move to more difficult Sudoku and then onto advanced Sudoku techniques. For a recap of the Sudoku rules, checkout my previous post.