Techniques for solving Sudokus

The best tips and tricks for solving sudokus

Here you will find several techniques that we have been compiling that we hope will help you solve sudokus better and faster.

Solve a Sudoku

Techniques 1: First Tips

Let's start by reviewing the basic rules of the game:

In this first lesson we will expose some useful tips when solving sudokus.

  1. Use a pencil. It is much more comfortable to make a sudoku in pencil than on a computer screen. In addition, the pencil allows you to erase it in a simple way.
  2. Practice gradually. Usually many newspapers and magazines do not catalogue sudokus because of difficulties so, for a neophyte, it can be really complicated to finish a complex sudoku. At PrintSudoku.com we catalogue sudokus so that you can practice with sudokus according to your level. The higher the level the more difficult it will be (usually) to put the numbers and, in the case of the very difficult ones, sometimes you will have to try plays.
  3. To test plays there is nothing better than typing the candidate numbers in the upper left corner of the cell. If you write small or in a margin, as you discard numbers, strike them out.
  4. Take it easy, sudoku is a relaxed game. Some sudokus can be resolved in a matter of minutes but others may take hours or maybe days.
  5. Well-designed sudokus have a unique solution, use this feature to your advantage.
  6. Never feel until you have finished carefully examining all the possible moves.
  7. Follow an order in the placement of the numbers, a good tactic is to start with the numbers that appear more frequently ending in the less frequent; in case of ties decide the order and follow the whole game.
  8. Check that every step you take is valid, a failure at first can be disastrous.
  9. If you don't find a possible solution, ask for help, or try sudoku at another time. Many times the solution appears when you least expect it, and not always when you are in front of the sudoku. ;).

Techniques 2: Basic Method

The easiest way to discover a number is when there is only one number left in a row, column or quadrant. In this case the missing number goes into the only empty box.

Lesson 2

As you can see, the first row is located all the numbers but the 7, so in the empty cell you can only go this number. In the first column something similar happens with 5, just like in the sixth quadrant with 1.

Techniques 3: Crossing by row and column

Another way to discover numbers is to cross by row and column. This consists of focusing attention on a square and checking which numbers can go in that position, eliminating those that are in the same row or column.

In the following image we can verify that in the indicated box only the 7 can go, because the numbers 1,8, 3, 6 and 9 are in the same column and the numbers 2, 4 and 5 in the same row.

Sudoku Technique 3

An improvement of this technique is achieved by also controlling the numbers that are in the same quadrant. In the following example we can see that using the cross between rows and columns we would have the candidates numbers 5, 7 and 8 to place them in the marked box. Since the numbers 5 and 8 are already placed in their positions within the quadrant, we can discard them, so the number 7 is the one that occupies the indicated position.

Sudoku Technique 3

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