User blog comment:QuasarBooster/Bashicu matrix version 4 in Python!/@comment-35470197-20191109233117/@comment-35470197-20191110015021

> Aren't all ancestors of an entry less than that entry (besides the entry itself)?

Yes.

> Once you're at the top row, you just have to check if the one entry is less than the other.

In that algorithm, how about the 1-rowed matrix (0,1,2,1,2)? If I correctly understand what you wrote, isn't the first 1 an ancestor of the rightmost 2?