It_Wasnt_Me's blog

help in geometry problem
By It_Wasnt_Me, history, 5 years ago, In English

552D - Vanya and Triangles in this problem, shortly you should count all number of triangles with non-zero area.

My idea was to count all triangle I could which is NC3 then I will subtract zero-area triangles

zero-area triangle will occur if there is 3 points on the same line(horizontal, vertical) or have same diagonal.

Unfortunately I received (Wrong answer) and I can't prove why my solution is wrong, I tested it on several testcases and it gives Right answer.

https://ideone.com/iiuxuP Any help

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5 years ago, # |
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You can try the following input:

3
-2 2
0 1
2 0

Your code prints 1, the correct answer is 0.

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    5 years ago, # ^ |
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    Edit: I was wrong, sorry. Yes the solution doesn't take care of all colinear points.

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