pratikmoona's blog

Geometry Problem
By pratikmoona, 14 years ago, In English
could anyone please tell me the error with my code? It is giving wrong answer.

QUESTION: http://livearchive.onlinejudge.org/index.php?option=com_onlinejudge&page=show_problem&problem=3109

CODE: http://paste.bradleygill.com/index.php?paste_id=290688

The question is from an ACM-ICPC regional.
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14 years ago, # |
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Recommendations to solution – Playing Field

- Type: Precomputation, coordinate geometry
- Cannot find the area on the fly for all Q
- Precompute the area of all polygons with a segment joining 0 and x as end points.
- We can do this by using area of [0,x-1] and area of triangle [0,x-1,x]
- To find area of given polygon we need to add/ subtract the precomputed areas and 1 triangle (how?)
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  • 14 years ago, # ^ |
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    That is what I did.

    The area[i] stores the area of the polygon which has vertices from 0...i (area[n-1] has the final area)

    To find the area of the region from vertices u to v, it is abs(area[v] - area[u]) - area of triangle which has vertices(v, u, 0).

    The complexity per test case is O(n + q).
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  • 14 years ago, # ^ |
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    Wait, in what cases would we have to add the precomputed areas?
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