Shouldn't step 3 in your algorithm description:

|S(e)| <= |S(f)|

read

|S(e)| > |S(f)|

? (Not having been a Math major, of course, could lead me to misinterpret "|S(t)|", which here I'm interpreting as "the size of set t".)

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Anyway, I had intended to suggest an algorithm dealing with sorting based on the lengths of line segments, but I now realize that's probably not much use in this case (since vroom wants to find the clumps, not necessarily a point). And reading further down the page, I like Ntromda's idea, but I, like him/her, wouldn't know how to begin coding it (without thinking about it for a long while...).