It is Easy to Learn How to Play Sudoku

My easy to understand illustrated techniques teach you how to play Sudoku puzzles. In several articles, (just too much to show in one article) I will share with you how Sudoku puzzles are solved.

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In this article, you will learn the basic techniques on how to play Sudoku puzzles and games. When the challenge gets tougher, read my article on

Sudoku Tips. Apply advanced techniques such as X-Wing and Swordfish to break the logjam of the most difficult puzzles.

Sudoku is solvable. A properly prepared puzzle only has one solution. There isn’t any need to guess (although you will be tempted at times). Applying simple logic and eliminating candidates will provide the solution in every case.

Math is not required to play Sudoku. You could play Sudoku using any nine symbols or colors. Numbers just happen to be easier.

Sudoku In a Nutshell

Traditional Sudoku is a 9×9 puzzle grid made up of nine 3×3 regions. Each region, row, and column contains nine cells each. See the example below.

Sudoku Puzzle

Sudoku Puzzle

The numbers shown in the example are the “givens”. These numbers can not be changed in any puzzle.

You solve the puzzle by filling in the empty cells with a single number (from all the possible candidates) that doesn’t violate Sudoku rules. There is only one correct number per cell.

Scan the “givens” looking for the same number in different rows, columns, or regions. Eliminate cells for consideration by applying the Sudoku rules using these numbers.

In cases where the solution isn’t immediately obvious, you markup or pencil in a vacant cell the possible candidates for future reference.

Consider using the blank Sudoku grid with candidates method to determine all the possible candidates. This can save you time in solving puzzles and prevent missing important candidates. It will also reveal answers that are not immediately obvious otherwise.

After you have identified the possible candidates it is time to apply some logic. It is necessary to eliminate all candidates to arrive at a single answer for each cell. I’ll cover this topic in more detail in related articles.

The Sudoku Puzzle Challenge

Complete the Sudoku puzzle so that each and every row, column, and region contains the numbers one through nine only once.

The puzzle above I would rate it as very easy. I hand-crafted this puzzle. It can be solved using simple logic and eliminating a few candidates.

It is interesting to note that it is not the quantity of givens that make a Sudoku puzzle easy or hard. Rather, it is the location and combination of givens.

How To Play Sudoku

Sudoku Puzzle Scan For Ones

How To Play Sudoku Puzzle Scan For Ones

In this example on how to play Sudoku, we begin playing Sudoku by scanning the puzzle.

It doesn’t matter where you start. I suggest looking for the number that has several “givens”. The more givens of a particular number often means that it will be easier to solve.

In this case you can see that there are three number ones (1).

Applying the Sudoku rule, you know that a 1 can not go in any row, column, or region that already has a 1. Plus you know, that every row, column, and region must have a 1.

The scans are marked with red arrows in this example. The two parallel scans from the two ones in the middle tier prevent any ones in the top two rows of the left most region. The vertical scan eliminates the middle cell of the bottom row from consideration.

In this example, you can see that there is only one cell (marked with a black X) that can contain a 1 in the left most region in the middle tier. Enter a 1 in the cell marked with an X.

Now that a cell is solved, you should look to see if it will help us solve another cell or two. In this case there aren’t enough clues to solve for ones at this time.

Likewise there aren’t enough clues using this method for twos or threes at this time.

Let’s look at the fours for your next lesson on how to play Sudoku.

Sudoku Puzzle Scan For Fours

You can see a similar pattern in the fours as there was in the ones above. In the lower left region you can see that there is only one cell (marked with an X) that isn’t eliminated using the scan method. Enter a 4 there.

See if you can find the rest of the fours. You have enough clues.

Now continue solving for fives through eights. Your grid will look like the next graphic in the center of your grid.

Naked Nine

Naked Nine Sudoku Solution

Can you find a nine in the example at the left without using any other numbers to help?

Yes, you’re right. A nine goes in the middle row to complete the row. It is the only missing number. That was simple!

The Sudoku Solution So Far
Sudoku Puzzle Partially Solved

You are making great progress in learning how to play Sudoku. You should be able solve most cells using the scan method you learned so far.

The image on the left was solved using just the scan method and entering the naked nine as mentioned earlier.

Pencil In Candidates

Let’s say you are stuck. It’s time to pencil in all the possible candidates for the remaining cells.

The example on the left shows all the possible candidates for the partially solved puzzle.

You can quickly note that in the seventh column are two “naked” single numbers standing alone.

The naked numbers are 1 and a 2. We also have a “hidden” 6 in the same column.

Since the 1 and 2 are already found, you can eliminate the 1 and 2 from the cell containing 1, 2 and 6. The 6 remains. Enter these numbers and you have quickly completed the column.

Now that you have found a 1 in the seventh column, you can eliminate the 1 from the last cell in the bottom row. (left most region)

A 3 remains. Enter the 3 and you have completed the bottom row.

As you enter a found number, be sure to cross off that number in the row, column, and region that your found number is in. As you do, new “naked” numbers will appear.

In the lower left region, when you entered a 3 solving the bottom row, enables you to now eliminate all threes in this region. Doing so reveals another “naked” 6 and a 1/6 pair. Enter the 6 where the “naked” 6 is.

Now you can also remove the 6 from the last cell in this region. A “naked” 1 remains. Enter the 1 and you have solved this region.

Congratulations! You now know how to play Sudoku (at least an easy one)! Try a harder game of Sudoku now.

Be sure to read my other articles on how to play Sudoku.

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All Pages on Solving Sudoku Puzzles

Math

by Rick Yakubisin(Greensburg, PA) Any row, column or grid. Pick a candidate and count how many the chosen candidate is in the row, column or grid. Count the cells that

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Chain

To use the chain strategy, pick a box with only 2 candidates that you would like to solve. Now imagine that the answer to that box is the first candidate.

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Row of 3

by RFTredwell(Orono, Maine, USA) Suppose you have solved three cells in a row (or column) within a region. (Rows with letters, from top; columns with numbers from left.) For instance,

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Using Colors

by Mohammed Hajooze(Aleppo Syria) First I use Orange to mark the start of color mapping, in this example the candidate is (1). Find a column or row where the candidate

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Rule of Two

by Cynthia Wilson(White Sulphur Springs MT USA) For difficult puzzles, I’ve adopted what I call the Rule of Two. Simply put: no cell should ever have more than two numbers

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Programming Sudoku

How to Program Sudoku Programming Sudoku is a challenge for computer programmers. Could a little advice help you in creating your next masterpiece? Several programmers have contacted me in the

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