# Sudoku Solving Techniques: The 9×9 Grid Puzzle Game

Sudoku is a logic-based game. It helps in keeping your brain actively working. It is a kind of mathematical puzzle in which you have to fill the rows and column with the digits starting from 1 to 9. The only rule which has to be followed is that no same row, column, or nine 3×3 subgrids have the same digit twice. There are many ways or techniques available to solve Sudoku puzzles. Easy Sudoku puzzles are solved by the method of elimination. However, more strategy and logic is needed in solving the difficult ones. Below given are few techniques or way to solve a Sudoku puzzle. The first three in the list below are essential and basic techniques to solve a Sudoku puzzle. The rest is a bit more advanced in nature.

Hidden Single:

Hidden Single Technique is the most basic and common technique to solve a Sudoku puzzle. It is the first step to in solving the Sudoku puzzle. In the process of determining where a digit should be placed in a column, row, or a 3×3 grid, we find that there is only one cell where that particular digit can go. Hence, it has to be there in that particular cell only.

Naked Single:

Naked Single is another very basic form of techniques which helps a solver in solving the online Sudoku puzzle. While thinking of which digit of 1 to 9 to be placed in an empty cell, the solver would first search out what all digits have appeared in the common column or row or the 3×3 grid. If in all these cells eight out of the nine digits have been used then the digit which is left should be placed in that empty cell.

Locked Candidates:

When a solver is examining a 3×3 grid box, they might found that a particular digit is locked in a specific column or row of that box. The exact position cannot be determined yet. This method tells us that such a digit cannot appear in other positions of the same column or row.

X-Wing:

If there is a number which is a candidate for exactly two cells in two different rows and the columns of those two cells in those two different rows are exactly the same, then that particular number cannot be a candidate for any other rows in that same two positions or columns.

Swordfish:

Swordfish technique is a general form of the X-wing technique. Is a number is a candidate for maximum three cells in three different rows such that their position occurs in exactly three different columns, then that particular digit cannot be a candidate of any other row in the same three columns.

Nishio:

The logic behind the Nishio technique is similar to that of the proof of contradiction method in mathematics. Assume that an undetermined cell is a place for digit “k”. If this assumption leads to a contradiction, then we will be able to know that the assumed digit is incorrect. The result of which will be that particular cell will not contain that digit “k”. Hence, the digit can be removed from the cell as a candidate.

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Sudoku is one of the best logic based games ever played. The above-given techniques might help or provide a solver base to solve the required Sudoku puzzles a way more easily.