How to Solve Sudoku Puzzles Quickly and Reliably?

Sudoku is very like mathematics. As soon as you start understanding it, the answers come to you. Here you can know what the game is and how you can solve Sudoku puzzles quickly and reliably.

Sudoku Game

Sudoku is a logic-based puzzle in which numbers must be placed at the right time and place with an aim to fill a 9 by 9 grid. In such a manner that every row, column and line with 3 by 3 grids have all of the digits from 1 to 9. Seed numbers are always provided to help a player reach this goal. A true Sudoku online puzzle always has one solution and no ambiguity. Some variants of the game include Killer Sudoku, Mini Sudoku, Cross Sums Sudoku, etc.

The Rules

The numbers can’t be repeated in columns or rows or nonet, but they can be repeated diagonally.

The sum of all numbers in a row, column or nonet needs to match the small number printed in the corner.

How to Solve a Sudoku Puzzle?

There are two ways of solving Sudoku online or offline puzzle that are mentioned here, Crosshatching and Penciling.

The First Method — Crosshatching

In this method, you will consider a single nonet and fill it by remembering that every number will appear only once in each row or column.

How to Get Started?

You can start the puzzle anywhere, but it is recommended that you work your way from left to right and top to bottom. If the first cell is labeled as A and the last is named as I in this example. So, you should focus on nonet A and then you will see 5 numbers are missing in this example, 1,5, 6, 7 and 8. You should then try to place each of the missing numbers in the empty cells.

Crosshatching for 1 (Nonet A)

When you try to place number 1, you will realize that you need to cross out all columns and rows that contain the number 1 and pass through A nonet. By using this technique, you will be left with just three empty cells.

Crosshatching for 5 (Nonet A)

The next step is to try to place number 5. When you do that, you will again need to cross out all rows and columns with 5, and you will be left with three empty cells. So, again, you need to move to the next missing number.

Crosshatching for 6 (Nonet A)

Now, it’s time to try and place number 6, when you do that, you will be left with three empty cells again which means we are still far away from the right answer.

Crosshatching for 7 (Nonet A)

When you try and place number 7, you will be left with just two empty cells. Yes, it’s progress, but you are not there yet.

Crosshatching for 8 (Nonet A)

Again, you should try the same method with number 8, and you will be again left with 3 empty cells.

No Numbers in the First Nonet

Yes, you have now tried all the possibilities of numbers in your first nonet, but you have made no progress so far. But hang in there, you will get results soon enough. Don’t expect instant answers and hold on to your patience for a bit longer.

Crosshatching Nonet B

Now, if you are feeling a bit more motivated then you should start crosshatching for nonet B. Here’s what you need to do.

Crosshatching for 1 (Nonet B)

When you try to place number 1, you will be left with just one empty cell which means you have just placed your first number. Congrats Champ!

Crosshatching for 2 (Nonet B)

Pumped with your success, you should try to place number two, and you’ll not be able two as you are left with two empty cells.

Crosshatching for 3 (Nonet B)

When you try placing 3, you will be again successful!

Crosshatching for 5 (Nonet B)

And you will be third time lucky by placing 5 as well.

Crosshatching for 2 (Nonet B)

As you have now filled every box in nonet B except one, it is obvious that number 2 should go in that empty box.

Success Mantra

Now, if you continue to apply the crosshatching technique in the same way you have done now, to nonets C to I, you will complete your first Crosshatching pass, and this will be your puzzle status.

The Second Method — Penciling In

If you continue to use the crosshatching method, you’ll surely solve the Sudoku puzzle perfectly. But now it’s time to learn about the second Sudoku technique, Penciling In. As the name suggests, this process includes writing down all possible candidates of a cell in empty cells of a given nonet and then use crosshatching to cut off all numbers that don’t fit. Have a look at how this is done here. ‘

Penciling in Nonet A

As you might have guessed we start by penciling in Nonet A and you will soon realize that again 1, 5, 6, 7, and 8 could be put in there. This time, you have to write all these numbers at the top of each cell within nonet A like shown below.

Once you have written the numbers in each of the empty cells, you look down each column and row for matches. When you have a match, you can cross out the matching number in the cell. Though you might think that this method is very like Crosshatching you did already, but it is a fact that when considering multiple cells, it yields more insight. Have a look at what numbers you can cross off on the basis of the existing numbers in the rows.

The next step is to look at what numbers you can cross off on the basis of existing numbers present in the columns.

By using the penciling in method, you can easily fill in 8,5 and 1. As penciling in numbers effects what cannot or can go in the remaining empty cells, you can repeat the Penciling in process for Nonet A.

If you have been following the crosshatching and penciling in efforts, you would have completely filled nonet A and B by now and have made good progress.

Keep Going

Now you just have to keep going towards your goal of filling in all empty cells by following the aforementioned methods. To help you in the end, here’s the complete puzzle, fully solved. But look at it when you are done and wish to cross check the results. If the results don’t match, you should double check your efforts and find where you went wrong. If they do, you have learned how to solve puzzles quickly and reliably. Now you can keep going and play Sudoku with LiveSudoku where puzzles are more interesting than you can imagine.