Problem 1387. Points on a circle.
This problem is related to 1283, Points on a Sphere. In this case, instead of a sphere, you have a circle. Given a radius R, calculate the number of points on the circumference of the circle that have two integer coordinates. For a circle of radius 5, you would have 12 points:
- (0, 5) and (0, -5)
- (5, 0) and (-5, 0)
- (4, 3) and (4, -3)
- (-4, 3) and (-4, -3)
- (3, 4) and (3, -4)
- (-3, 4) and (-3, -4)
Some radii are quite large, so watch out. Good luck!
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4 Comments
Great problem! Learned a bunch from others solutions as well.
In the problem statement, I think you meant '3' and '4', rather than '1' and '2', in the respective +/- combinations.
Thanks for catching my stupidity on that one, HH. It's fixed now.
The tip for this question is the sum of squares function, which I use in my solution. There are many possible solutions to this problem, but the huge circle radii limit what we can employ, so be careful.
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