In order to solve simple Sudoku puzzles, all you need is a bit of patience and care. Let's look at some examples. Look at the picture below. In the first cell of the last row, it is possible to set only number 1 because numbers 3 and 4 are already present in the column and number 2 is in the blue block. You can then select the number for the second cell of the third row. This way you can solve this puzzle to the end. As you can see, there is no big deal.

But more often, you come across puzzle of size 9x9, and what do you do if you can not find the cell for which you know the right decision? In this case it is recommended to find a list of candidates for each free cell. The candidate is a value that is acceptable for some cell at this stage of the puzzle solving. The figure below shows an example of the candidates finding.

After this, you can apply the following tips for solving Sudoku according to puzzle difficulty.