Whether you are a Sudoku beginner, an intermediate player, or an expert at breaking through the sudoku puzzles, every player gets stuck in the game at some stage. Applying logical reasoning rather than guesswork is the key to solving a sudoku puzzle irrespective of the difficulty level.
Solving sudoku puzzles in a systematic way requires sudoku solving techniques. Here are some basic sudoku solver techniques and sudoku hints that will help you when you play sudoku online:
Sudoku Hints for Beginners
If you are a beginner, you should start with easy sudoku puzzles, which can be solved with basic techniques.
Identify the obvious cells
You can easily identify a row, column, or 3×3 section with one or two blank cells in the simplest puzzles. You can easily find solutions for these cells by identifying the missing number.
Use the Scanning Technique
The easiest way to start a sudoku puzzle is by scanning rows and columns within the triple-box area. The scanning technique helps eliminate the numbers and cells to find situations where only a single candidate will fit in a particular empty cell. Use these two scanning techniques to solve the puzzle:
Scan in one direction
In the below example, let’s take the first three boxes. If you scan horizontally, you will find the number 8 has been used in the second and third 3×3 boxes. This means that 8 cannot be placed in the second and third row of the first 3×3 box. This leaves the first row to place the number 8 and only a single square to fit the number.
Scan in two directions
In the same example, we can also use the scanning method using the perpendicular columns and rows. If you scan the rows of the first and fourth 3×3 boxes, you will find that row 1 and row 5 contain the number 1. You can also see that row 8 contains the number 1 in the eighth box. Therefore, if you have to place 1 in the seventh box, there’s only one cell where you can place 1, in row 7 and column 2.
Sudoku Hints for Relatively Harder Puzzles
When the basic sudoku solving techniques are exhausted, and the simple steps can’t reveal the solutions, here are the techniques you can use:
You may often find a cell where only a single number will fit because the other candidates are already used in the corresponding row, column, and the 3×3 box. For instance, the fourth box already has 3, 4, 7, and 8. Also, the column corresponding to row 4 column 2 has the numbers 9 and 5 while the corresponding row already has 1 and 6. Candidate number 2 is the only one remaining, which is the solution for row 4 column 2.
Eliminating numbers from rows, columns, and 3×3 boxes
The process of elimination comes in handy to solve the harder puzzles with ease. Taking an example from a puzzle, row 8 column 3 contains 1, which implies 1 cannot be placed in that row. In the eighth box, 1 may be either placed in row 7 column 5 or row 9 column 5. Looking at the second box, the remaining place for 1 is in row 2 column 4.
Eliminating cells with naked pair
There are two ways of doing this, eliminating naked pairs in a box and eliminating them in a row or column. In the below example of using naked pairs in a box, we can see that candidates 4 and 9 can only fit in row 7 column 3 and row 8 column 3 of the seventh box. Further, 6 cannot fit in column 8 of the seventh box. The only place where candidate 6 can fit is in row 9 column 2.
Similarly, using naked pairs in a row or column, we can find a solution. For instance, in the eighth box, row 9 is the only place where candidates 2 and 7 can fit in the row. Considering row 9, the number 6 already exists in the ninth box and in column 1. This leaves out row 9 column 3 as the single-cell for candidate 6.
Eliminating cells with hidden pairs
If you find two cells in a box contains a hidden pair that are not found in the remaining cells, you can safely exclude the other candidates from these two cells. For example, if two cells have 1 and 9 apart from other possible candidates, and these two candidates cannot be found in the other blank cells, the numbers 1 and 9 form a hidden pair. The other candidates can be removed from the two cells, and you can be sure that only 1 & 9 will fit there.
Eliminating cells with hidden triples
If you find three candidates restricted to three cells in a particular group, you can eliminate all the other candidates from these three cells. The three candidates are known to be a hidden triple. For example, the numbers 3, 6, and 7 can be found only in cells of three columns but same row. This technique implies that you can eliminate the other numbers from these cells.
Eliminating squares with hidden quads
Similar to the above situations, if you find four candidates restricted to four cells, the other numbers can be eliminated from those cells. Hidden quads are rarely found and difficult to spot. Nevertheless, you can use this technique if you come across a hidden quad.
Also Read: 5 Ways Sudoku Helps Promote Brain Health
Eliminating cells using X-wing
If you are a sudoku master and love attempting extremely difficult puzzles, you can use the X-wing technique in some situations. For instance, if you find a candidate can be placed in two cells of the same row or column and also in another cell with other numbers in the same column or same row, you can eliminate that candidate from the other cells.
Another variation of the X-wing that sudoku players can use is the Swordfish pattern. This technique is required only for puzzles that have a swordfish pattern. This pattern occurs when each of the three columns or three rows contains two or three cells with matching locked candidates.
Naked Triples & Naked Quads
The same technique that applies to naked pairs also applies to naked triples and naked quads. A naked triple occurs when 3 cells in a box contain only three specific candidates that also exist in other cells. In such situations, these three candidates can be eliminated from the other cells. In the below example, the numbers 1,6 and 4 form a naked triple in the top-left, bottom-left, and bottom-right cells. These numbers are also candidates of the highlighted cells. Based on this technique, you can safely eliminate 1, 6, and 4 from the highlighted cells.
Similarly, a naked quad occurs when four cells contain no other numbers than the same 4 numbers. In such a situation, you can eliminate the 4 numbers from other cells. For instance, in the below example, 2, 5, 7, and 9 can be found in the left column and the middle-bottom cell. The numbers 5 & 7 are also candidates in the highlighted cells. using the eliminating cells with a naked quad technique, these two numbers can be excluded from the top-right two cells.
The Bottom Line
Using these hints in a sudoku game can help you find multiple solutions to solve a particular puzzle. These techniques are used based on the difficulty level of the puzzle. You should always start with the basic sudoku techniques and move forward with the more complex techniques. Pick a cell randomly and start scanning rows and columns to identify the easy targets. The best way to solve the sudoku puzzles is by using pencil marks to mark the possible candidates and find the correct candidate values. The pencil marks are important for the eliminating techniques as you can place multiple candidates in a cell and erase them later when you find the correct solution.
You can play sudoku against a random opponent on the MPL app and use these sudoku solver techniques to crush your opponent. The sudoku games are time-based and require quick decisions to get a higher score. You can use these sudoku techniques to your advantage to find the solutions quickly and avoid entering incorrect candidate values. But, before you begin to solve sudoku puzzle, understand the sudoku rules and sudoku hints thoroughly.