Proven Sudoku
Techniques / Almost locked sets
Death Blossom
Also called Death Blossom pattern, Stem and petals.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
One square is the stem. Each number it could hold points at its own almost full group, like petals. If every petal rules out the same thing, that thing is gone whatever the stem turns out to be.
The exact rule, for stronger players
The rule, stated exactly: A stem cell whose every candidate has a corresponding petal ALS, each linked to the stem by that candidate as a restricted common. A digit common to every petal is eliminated from cells seeing all its positions across the petals.
What it removes: Remove the shared digit from cells seeing every instance of it in all petals.
Why it works: The stem takes one of its candidates, which locks the matching petal. Every petal contains the shared digit, so whichever petal locks, the digit is confined there.
Worked examples
None yet. This pattern does not turn up in our daily boards, so there is no real example to show. We would rather wait than draw a fake one.
Learn these first
- ALS-XZTwo of those almost full groups share numbers.
Related almost-locked sets
- Subset ExclusionThe same idea for any size of group.
- Sue de CoqLook where a row or column crosses a box.
- Sue de Coq (extended)The same counting trick with more squares involved.
- Aligned Pair ExclusionLook at two squares together and list every pair of digits they could hold.
- Aligned Triple ExclusionLook at three squares together and list every set of three numbers they could hold.
How often does it come up?
Our rough estimate: rare, and computationally expensive to search for by hand.