by Xwtek » Sat Apr 24, 2021 4:08 am
Alternatively, you can solve this using a bug technique.
if the candidate 5 in r9c2 and candidate 2 in r1c1 is removed, it will turn into a bug situation. So, either candidate must be present. And candidate 5 at r9c2 implies candidate 2 at r1c2. So, you can remove any candidates with digit 2 at row 1 and the top-left home, except for these two solutions.