When you've ruled out one of your notes, click on it again in the Notes box.

Click here to see the video of how it works.

If you'd like to repeat a note (notes) in another square, simply drag the number from the original square.

Clicking will get rid of all the Notes in the square.

Clicking will place all possible Notes in the square.

Hints: Also in the candidates bar are, :

Narrowed it down to a couple of numbers but still not totally sure? Click the numbers you want from the Notes box.

Ready to fill a number in that square? Just click the one you want in the number ring.

Show up on the left side above the grid as the 'Notes' box. A 'number ring' appears with that grid's possible numbers. This might have some copyright issues as 'derivative works', but that's not a programming concern. If this isn't producing 'interesting' enough puzzles, then you can take the 'cheat' approach, which is to have a database of existing hand-created puzzles, then choose one and scramble it by randomly swapping rows and columns, or swapping digits. Because each cell that you removed was able to be deduced at the time it was removed (because it was the only possible value for the cell once the cell was empty) then the player should be able to solve the puzzle by adding the values back in the opposite order to which they were removed. You can repeat this until you have removed a desired number of cells. To verify this you need to compute a list of valid values (values that aren't present in other non-empty cells in the same row or column) for each cell in the row or column that the cell is in, and even if the cell contains more than one possible value, if it is the only cell in its row that contains that value in its list, or the only cell in its column, then the value can be determined and so you can remove it.

if there is only one possible value (the value in the cell) then you can remove itĪnother way that the value of a cell could be deduced is if it is the only cell in its row or column where that value is possible.calculate the valid possible values for that cell based on the other non-empty cells in the grid.When removing the numbers in step 7, inside a loop:

So you need to write a function that computes a list of the valid values for an empty cell, using the constraints (you just need a list of all values that aren't present in the same row or column). In other words at each point it should be possible for the player to logically deduce the value of at least one cell without guessing. However, step 7 is more complicated than it seems, because you need your puzzles to be solveable. You will always end up with a valid result. changing all the 5s to 3s and vice versa). So just start of with the regular grid, then inside a loop just generate pairs of random rows and pairs of random columns, and swap them. You can also swap two columns and still end up with a valid grid, e.g swapping columns 2 and 4: 1 2 5 4 3 Then, if you swap two rows, you will still have a valid grid, e.g. You can replace steps 1-6 by starting with a known valid filled grid, and then applying transformations to it that keep the constraints intact.įor example, you can start off with this grid, which is easy to generate by setting grid to ((i + j) % 5) + 1: 1 2 3 4 5

Easy sudoku printable 5x5