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Death Blossom

Points. A Death Blossom consists of a "stem" cell and an Almost Locked Set (ALS) for each of the stem cell's candidates. The ALS associated with each candidate of the stem cell has that digit as a candidate, and every occurrence of that digit in the ALS can see the stem cell. The ALSs can't overlap i.e., no cell belongs to more than one ALS. Also, each ALS must have at least one digit that is not in the stem cell.  What Sudopedia Says.


Death Blossom Example 1. The first example is from the Sudopedia website. The stem cell is the vi-value cell (18)r1c9. It connects to 2 ALS each with 3 cells, one in r5 and the other in c5. It eliminates the red candidate 5r5c5.


In terms of cover logic, a death blossom is simply an ALS chain. This example has 7 cell truths covered by 8 cover links. Two cover links overlap in r6c5 to eliminate 5r5c5.


(See logic diagram below)



Death Blossom Example 1, 3D View. In this 3D view of the Sudopedia example, it's easy to see that the Death Blossom looks like a chain that has ALS on either end. This example looks like putting the eye of one needle through the eye of another needle.


Death Blossom Example 2. The second example has a stem cell r2c8 with digits 2 and 3, which connect to two column ALS. The ALS in column 3 is shaded green and the ALS in column 5 is shaded red. Digit 9 in r5c3 sees both and is thus eliminated.




Death Blossom Example 3. The third example has a stem cell in r1c6 with digits 2 and 9. Each ALS has only two cells. The ALS in column 4 is shaded red and the ALS in column 6 is shaded green. There are two eliminations, each contained in a different box/column pair, r3c6 <> 8 and r6c4 <> 8.




Death Blossom Example 4. The fourth example also has two eliminations but they are different digits. The stem cell with digits 2 and 5 is in r7c9 and the 2 ALS are in row 5 and cloumn 6 respectivly. Digits 6 and 8 see all examples of digits 6 and 8 in both ALS, and are thus eliminated.


Death Blossom Example 5. A single box/row overlap eliminates two candidates.

Logic Diagram, Death Blossom Example 1.


     (5c5)  (6c5)  (3c5)  (1r1)  (8c9)  (7r5)  (1b5)  (5b5)


3N5: 5r3c5==6r3c5==3r3c5                                    

       |      |      |                                      

7N5:   |    6r7c5==3r7c5                                    

       |             |                                      

1N5: 5r1c5=========3r1c5==1r1c5                             

       |                    |                               

1N9:   |                  1r1c9==8r1c9                      

       |                           |                        

5N9:   |                         8r5c9==7r5c9               

       |                                  |                 

5N4:   |                                7r5c4==1r5c4==5r5c4 

       |                                  |      |      |   

5N6:   |                                7r5c6==1r5c6==5r5c6 

       |                                                |   

2V1: 5r6c5----------------------------------------------+