Sudoku HowTo

# Standard Notation

Standard Notation is a way to describe Nice Loops and other chains using text.

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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