The puzzle master disappointed me on part 2. At least for my input, none of the nodes appear at locations where an intermediate antinode would appear between them. For example: if you have nodes at (1,4) and (7,1), you would also get antinodes at (5,2) and (3,3). But he took the time to generate locations so that each pair’s Δx and Δy have no common factor.
I know I have no right to complain, as he kept the problem relatively easy (it’s still day 8) and I arrived at the correct answer. But I wasted time being a tad too clever and I just know he’ll pull something like this later in the month when I least expect it. Happens every year.