I had quite a time doing day6 because after I computed all of the distances for all the areas for each given vertex, I could not eliminate the infinite vertices mathematically. For the 6-vertex the removal of infinite vertices was simply a matter of finding the convex hull using transitive closure, and then removing those vertices. But in the real data set, that was not enough. From reading a comment on reddit.com (link below) I gathered that one way to have found the set of all infinite areas would have been to give the total area a large border so that the infinite areas seemed infinite because of their disproportionately large area.
https://www.reddit.com/r/adventofcode/comments/a3kr4r/2018_day_6_solutions/ But I did not try that because I discovered how to use viewmat to see the 50+ areas and to use j's Amend on the array of minimum distances to superimpose selective vertices as dots on the viewmat. Then I could see (most of the areas -- not all of them because the color differentials were not very contrasty for my color-defective eyes) the areas and visually chase down the largest area. The viewmat approach mesmerized me a little, to be honest, but I am wondering if another more mathematical approach could be used? I would be happy to share my existing code, if that would be a better place to start. But perhaps my description of my and your approach would be adequate. Thanks, -- (B=) <-----my sig Brian Schott ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
