int main() {
	{
		//Wrong
		set  s = {1,2,3,4,5};
		auto it = s.lower_bound(3);
		s.erase(it);
		it++;
		printf("%d\n", *it);
	} {
		//Correct 1
		set  s = {1,2,3,4,5};
		auto it = s.lower_bound(3);
		s.erase(it++);
		printf("%d\n", *it);
	} {
		//Correct 2
		set  s = {1,2,3,4,5};
		auto it = s.lower_bound(3);
		it = s.erase(it);
		printf("%d\n", *it);
	}
}

Hi, Codeforces!

I'm looking for some problems which C++ STL 'set' can be used effectively for.

Thanks!

You can see the problem here.

Every two circles touch in at most one point (in particular no circle can be contained in a different circle).

Does anyone have some ideas about the problem?

1. Smallest Enclosing Circle : 2-Dimension Problem (Written in Korean. Output is the smallest enclosing circle's position on the first line and the radius on the second line.)

2. Smallest Enclosing Sphere : 3-Dimension Problem

Thesis Link

Let P(X, Y, Z) = (Average(x(i)), Average(y(i)), Average(z(i)))

Average(x(i)) = Sum(x(i)) / N

Average(y(i)) = Sum(y(i)) / N

Average(z(i)) = Sum(z(i)) / N

P is inside of the points' convex hull.

Now find the farthest point(M) to P.

Move P toward M a little bit and the ratio should be small and decreasing.

If there is no such a movement, that is the answer.

Total Time Complexity is O(N * constant number)

(We can reduce 'N' by getting convex hull.)

My 2-Dimension Problem's Solution Code

My 3-Dimension Problem's Solution Code