Perfect Your Sudoku Style: A Guide to Winning Strategies

Sudoku is a popular activity with tons of benefits. Solving sudoku puzzles increases brain health and memory. Besides that, it’s fun, and it can be done anywhere.

Getting started at sudoku can be somewhat easy, but as you move forward, more difficult puzzles will require you to make use of advanced strategies.

How to Choose the Right Sudoku Technique

The appropriate technique depends on the player’s level. For beginners solving entry-level puzzles, checking blocks, columns, and rows should be enough. As players move forward, they’d need to start experimenting with more advanced strategies.

Your Guide to Fundamental Sudoku Techniques

In this guide, we’ll cover six different techniques: from the most beginner-friendly to expert strategies that should only be used in extremely challenging puzzles.

Penciling Candidates

The technique entails checking all possible numbers for each cell and preliminarily placing them in cells. Some cells will only have one option, and you can then discard the less likely ones, or validate the correct options. Penciling candidates is also the basis for more advanced techniques, as we’ll see below.

In physical sudokus, it’s advised to write the candidates lightly with a pencil, so you can erase it later. Digital puzzles usually allow players to write candidates in a smaller font.

Box-Line Reduction

This strategy is the next step after penciling candidates. After placing all the possible candidates in all cells, users should look for numbers that appear a few times in a row, column, or box. By cross-checking these parameters, you can dismiss non-viable candidates. For example, if you have three instances where 2 is a candidate, you can confront this in the applicable boxes and check which ones are more likely to be correct.

X-Wing

Moving to more advanced techniques, X-wing is a way of validating possible instances of a number and removing other candidates. It works by detecting an X structure among possible candidates, either in rows or columns.

For example, if you have two parallel columns or rows with various instances of possible 7s. And there are four candidates that make the X shape (this means the four candidates are aligned with one another). Then it means that 7 goes in either of these cells, for both rows or columns. This allows users to delete the other candidates.

Rarely Used Techniques for Advanced Solvers

Now we move on to more advanced strategies. These techniques can come in handy when other options are insufficient. Although they’re very useful, they can be hard to spot, or they complicate the puzzle, so they should be reserved for extremely challenging sudokus.

Swordfish

The swordfish is an advanced form of the X-Wing. Instead of looking for a repeated pattern in two rows or columns, it finds repetition in three sections. Once you spot these, it can help you clear out candidates from the remaining cells, as it’s certain that the number will be in any of these three cells for the corresponding rows or columns.

Furthermore, swordfish can be then boiled down to X-Wings, so it can be a good strategy to eliminate a couple of candidates before moving on.

WXYZ-Wing

The WXYZ-Wing takes it a few steps further. First, you look for a cell with four candidates, which we’ll call the base cell. Once you find it, you should check which of the candidates repeat in the corresponding rows, columns, and blocks. Usually, this will lead to three numbers repeating in all instances (blocks and rows), and one number that we’ll call non-restricted.

The non-restricted number will be repeated in the same block and the base cell, but not on the other corresponding rows or columns. This will let you eliminate the other candidates in the block.

Nishio

Nishio is a rather risky technique in sudoku. It implies picking a cell with few candidates (ideally two) and choosing one as the valid option. Then you’d move from there and start solving the puzzle under the assumption that it’s correct.

It could be proven to be false in a few moves, thus resulting in the other option being right. But it’s also possible to continue solving the whole puzzle and finding out it’s wrong in one of the last moves. That’s why this technique should only be used in extreme cases.

Apply These Strategies to Your Next Puzzle!

The strategies covered here should be useful for players of any level. If you’re just starting or consider yourself at an advanced level, keeping this in mind can help you improve.