Question

G’day everyone,

I have a 2d graph which has some points plotted on it.
What I need to do is get only the outer most points so that I can connect them up (isn’t really relevant).

What I can’t seem to wrap my head around is the algorithm that I need to use in order to do this?

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I think this might help you understand what I want to achieve:

o o o
o x o
o o o

All the o’s I want to get and the x I want to ignore. Also, the points can be in any position and any shape but I still want to only grab the outer most points.

Any ideas?

Also, I am not sure if this is the correct site to ask this on so if its not, please let me know where to go.

Thanks!

Answer 1

You need to do a convex hull of the set of points that you have. I personally prefer to use Graham scan for this as it is fairly easy to implement and has good computational complexity.