The cell names are enclosed in square brackets. This site uses the rncn notation for cell names. [r1c1] This is for row 1 column 1. Some people prefer the cell names written as [rc] using letters for the rows and numbers for the columns. [B2] would be row B column 2.

A link with strong inference is shown as =X=, where X is the value used to create the link. A link with weak inference is represented by -X-. The inferences are sometimes denoted with a + and - sign. +3 being strong inference on the value 3 and -4 being a weak inference on the value 4.

For looping chains a continuous loop will have a leading = or - to show the inference type from the last cell and trailing = or - to show the inference type back to the first cell. A discontinuous loop will not include any indication of the last or first links.

The example in Figure 1 shows a Continuous Nice Loop.

The standard notation for this loop is:

= [R1C3] -2- [R1C5] -1- [R3C6] =1= [R4C6] =3= [R4C1] =9= [R4C3] =4= [R3C3] =2= [R1C3] -

This would read something like - If R1C3 contains the value 2 then the value 2 cannot be placed in R1C5 because these cells are in the same row. If R1C5 does not contain the value 2 then R1C5 must contain the value 1 because the value 1 is the only other candidate in R1C5. If R1C5 contains the value 1 then the value 1 cannot be placed in R3C6 because these cells are in the same box. If the value 1 cannot be placed in R3C6 then the value 1 must be placed in R4C6 because R4C6 is the only other cell in the column that has the candidate 1. If the value 1 is placed in R4C6 then the value 3 cannot be placed in R4C6. If the value 3 cannot be placed in R4C6 then the value 3 has to be placed in R4C1 because R4C1 is the only cell in the row with the candidate 3. If the value 3 is placed in R4C1 then the value 9 cannot be laced in R4C1. If the value 9 cannot be placed in R4C1 then the value 9 has to be placed in R4C3 because R4C3 is the only other cell in the row with the candidate 9. If the value 9 is placed in R4C3 then the value 4 cannot be placed in R4C3. If the value 4 cannot be placed in R4C3 then the value 4 has to be placed in R3C3 because R3C3 is the only other cell in the column with the candidate 4. If the value 4 is placed in R3C3 then the value 2 cannot be placed in R3C3. If the value 2 cannot be placed in R3C3 then it has to be placed in R1C3 because R1C3 is the only other cell in the column with the candidate 2.

I guess it is good that there is a short hand way of writing this or I would be doing a lot more typing.

The example in Figure 2 shows a Dis-Continuous X Chain.

The standard notation for this loop is:

[R4C3] -1- [R4C6] =1= [R6C5] -1- [R1C5] =1= [R1C3] -1- [R4C3]

Notice there is no leading or trailing link indicator for standard notation on a dis continuous chain.

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Sudoku Rules and Techniques

Sudoku Rules

Acknowledgments

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

Sudoku Rules

Cross Hatching

Counting

Naked Set

Hidden Set

Claiming

Remote Pairs

X Wing

XY Wing

Simple Coloring

Fishy Things

Unique Rectangle

X Chain

Aligned Pair Exclusion

Forcing Chains

Finned Fishy Things

Almost Locked Sets

Counting

Naked Set

Hidden Set

Claiming

Remote Pairs

X Wing

XY Wing

Simple Coloring

Fishy Things

Unique Rectangle

X Chain

Aligned Pair Exclusion

Forcing Chains

Finned Fishy Things

Almost Locked Sets

Acknowledgments

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