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Comments on Queries to count points lying on arbitrary line

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Queries to count points lying on arbitrary line

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Suppose we have N points on XY plane, ie. (x, y) and x, y are integers and multiple queries where each query is of the form y = mx + c and m, c are integers.

Is it possible to count number of points that lie on the given line more efficiently than O(N) per query?

I believe some preprocessing might help or some data structure like QuadTree that counts points inside arbitrary rectangle.

The queries are offline so if it's possible using some batch processing technique or even SQRT optimization it would be better than naive brute force.

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2 comment threads

Are the points distinct? (1 comment)
Worst case or average case? (1 comment)
Worst case or average case?
trichoplax‭ wrote 11 months ago

When you use the notation O(N) are you looking for an improvement to the worst case performance or the average case performance?

My first impression is that your suggestion of a quadtree (or even just a regular grid) is likely to improve the average case, but not necessarily the worst case. I haven't verified this though.