Sudoku HowTo
Sudoku Rules and Techniques

Sudoku Rules




Acknowledgements

I would like to acknowledge these sites referenced for strategy ideas and solving techniques.

SudokuWiki.Org by Andrew Stuart
PaulsPages.co.uk by Paul Stevens
Sudopedia.Org

Box Claim or Row Column Claims

If all possible candidate locations for a given number in a given box are contained in a single row, that box can be said to claim the given number. All candidate instances of the given number in the row that are not in the given box can be removed.

This same process can be applied to a given number in a given box that is contained in a single column.
Box Claim. The example shown in Figure 1 shows all candidate instances of the number 1 in box 1 contained in row 1.

The number 1 has to be placed in one of the blue cells in box 1 so it cannot be placed anywhere else in row 1.

Any instances of the number 1 in row 1 that are not in box 1 can be removed.
Box Claim. The example shown in Figure 2 shows all candidate instances of the number 4 in box 7 contained in column 3.

The number 4 has to be placed in one of the blue cells in box 7 so it cannot be placed anywhere else in column 3.

Any instances of the number 4 in column 3 that are not in box 7 can be removed.
If all possible candidate locations for a given number in a given row are contained in a single box, that row can be said to claim the given number. All candidate instances of the given number in the box that are not in the given row can be removed.

This same process can be applied to a given number is a given column that is contained in a single box.
Row Claim. The example shown in Figure 3 shows all candidate instances of the number 9 in row 3 contained in box 2.

The number 9 has to be placed in one of the blue cells in row 3 so it cannot be placed anywhere else in box 2.

Any instances of the number 9 in box 2 that are not in row 3 can be removed.
Column Claim. The example shown in Figure 4 shows all candidate instances of the number 7 in column 5 contained in box 2.

The number 7 has to be placed in one of the blue cells in column 5 so it cannot be placed anywhere else in box 2.

Any instances of the number 7 in box 2 that are not in column 5 can be removed.
13 September 2014
by Armando Ramos,London
RE: Comments and feedback for claiming

your examples 1,2 and 3,clearly made me aware of the importance of removals. Many thanks
13 September 2014
by John
RE: Comments and feedback for claiming

Thanks for using the site. Good luck with your Sudoku solving

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This page last updated on September 16, 2011