This type of Alternate Inference Chain (AIC) starts and ends on a strong link for two different digits in two cells, which see each other. Therefore, the end digit cannot be in the start cell and the start digit cannot be in the end cell either.

Below is an example.

[B3]<>8 => [B3]=9 -> [B6]<>9 => [B6]=1 -> [I6]<>1 => [I6]=5 -> [H6]<>5 => [H6]=2 -> [H1]<>2 => [G1]=2 -> [G1]<>9 => [A1]=9. So we have the premise that if [B3]=9, then [A1]=9 too, but since [A1] and [B3] are in the same block, so [B3] cannot be 9 otherwise we will have a contradiction. And if [B3]<>8 then [A1] <>8 either, then no 8 will appear in Block at [A1] so [B3] = 8 and [A1]<>8.

Another example can be found below:

The notation is [C3]<>2 => [C3]=3 -> [C8]<>3 => [C8]=8 -> [C7]<>8 => [G7]=8 -> [G1]<>8 => [H1]=8 -> [H1]<>3 => [B1]=3. There is an obvious contradiction here that if [C3]=3 then [B1]=3 too. Since [C3] and [B1] are in the same block, they cannot both be 3 at the same time. So [C3] cannot be 3. We can also prove that [B1] cannot be 2 as well.

It's not easy to find examples applying this technique, so that no more examples are provided here.

See also: ««  Direct Elimination Techniques  »» ««  Candidates Elimination Techniques  »»