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Nunchucks |
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A Nunchuck is a forcing chain that includes Almost Linked Sets (ALS) and Finned Fish (including their Mutant Extensions). Basically, the Almost Linked Sets and Finned fish count as a node in the chain that is strongly connected to the fin and weakly connected to the potential elimination. If the chain uses alternating weak and strong connections, connects back in on itself, and the first and last connections are both weak, then the starting/ending candidate can be eliminated.
Consider the example on this page. The starting point is the 3 in green. This 3 is weakly connected to the 7 in the same cell, which is strongly connected to the 7 above, which is weakly connected to the 7 to the left, which is strongly connected to the 8 in the same cell, which is weakly connected to the 8 below, which is strongly connected to the ALS highlighted in yellow, which is weakly connected to the brown 3 in that box, which is strongly connected to the pair of 3's to the right, which are weakly connected to the 3 in green. Thus this 3 in green can be eliminated.
Look at the ALS in yellow. If the brown 8 were false then this would be a hidden subset causing the elimination of the 3 in brown. Thus the connection between the 8 and the ALS is strong, and the ALS to the 3 is weak. In this particular case the roles of the 8 and 3 could be reversed to show an almost linked naked subset, though that doesn't aid the forcing chain.
Sudoku Snake gives Nunchucks a skill value of 16000.
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