Saturday, May 11, 2013

project euler problem 165

Intersections

This is a good exercise to learn a little bit computational geometry.  I checked my old code. It takes 3.9 seconds to get the answer. I feels that my code is too slow but did not figure out how to speed it up. 

I checked the discussion, Robert_Gerbicz gave me an idea how to optimize. It is very simple, avoid using set or map when possible.  I followed his idea and removed set in my code, the run time is reduced to 1.4 second.

The set and map container are notorious in c++, probably because there was no hashset or hashmap available when STL was first published in 1990s.  I had a lot of experience that set and map caused a lot of coding and performance issues.

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