At how many points do at least two lines overlap?
Went a bit overboard I think at first, adding GCD and slope, was probably more than needed for part1, but will pay off for part2 ease. Essentially, I wanted to build a map of coordinates that lines touched, incrementing and filtering to get the answer.
All good, got 12, then remembered the part1 instructions of only vertical or horizontal lines. Perhaps just removing that filter will work for part2.
mix run
mix test