Burma

This is a generalization of the Swordfish (and the X-Wing).

Look for N columns with only C candidate cells for a given value, with N >= C.
If these fall on exactly N common rows, and each of those rows has at least C candidate cells, then all N rows can be cleared of that value (except the defining cells!).

Likewise for N rows with N common columns.

Some Burma patterns are listed below:

 Pattern name CNPossible placements
of the value in the pattern
Burma(1,1)Single Candidate 111
Burma(2,2)X-Wing 222
Burma(2,3)Swordfish 232
Burma(2,4)Jellyfish 242
Burma(2,5)Squirmbag 252
Burma(3,3)Burma 336

If we look to the possible placements of the value in the pattern we find some interessing properties. For an X-Wing we have 2 possibities, (one of the two diagonals of the surrounding rectangle). This also means, when we can place the value in one of the cells of the pattern, the other value can also be placed. Because, when we place a value two other candidates can be eliminated (from the same row and column), and only one candidate for the value is left. The same property works also for all the Burma patterns with 2 candidates. When we place one value, whe have a chain of eliminations, because each placement gives eliminations, and these eliminations generate new single candidates until the whole pattern is solved.

For the Burma(3,3) pattern we have 6 different placements. But now when we place one value, we get after elimination, a Burna(2,2) or an X-Wing, which gives us still 2 possibilies for the rest of the pattern. For each of the three cell of a row or a column of the pattern we have an X-Wing left, 3 X-Wings give us 6 possibilites.

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