Submission #969754

---

Source Code Expand

/*#include<bits/stdc++.h>
#define rep(i,n)for(int i=0;i<n;i++)
using namespace std;

int gcd(int a, int b) { if (!b)return a; return gcd(b, a%b); }
int main() {
	int n, k; scanf("%d%d", &n, &k);
	map<int, int>mp;
	rep(i, n) {
		int d; scanf("%d", &d);
		mp[gcd(d, k)]++;
	}

}*/
#include<bits/stdc++.h>
#define EPS (1e-10)
#define equals(a,b)(fabs((a)-(b))<EPS)
#define rep(i,n)for(int i=0;i<n;i++)
using namespace std;

struct Point {
	double x, y;
	Point(double x = 0, double y = 0) :x(x), y(y) {}
	Point operator*(double a) { return Point(a*x, a*y); }
	Point operator-(Point p) { return Point(x - p.x, y - p.y); }
	Point operator+(Point p) { return Point(x + p.x, y + p.y); }
	Point operator/(double a) { return Point(x / a, y / a); }
	double norm() { return x*x + y*y; }
};
typedef Point Vector;
struct Segment {
	Point p1, p2;
};
double dot(Point a, Point b) {
	return a.x*b.x + a.y*b.y;
}
Point project(Segment s, Point p) {
	Point base = s.p2 - s.p1;
	double r = dot(p - s.p1, base) / base.norm();
	return s.p1 + base*r;
}
double norm(Vector a) {
	return a.x*a.x + a.y*a.y;
}
double abs(Vector a) {
	return sqrt(norm(a));
}
typedef Segment Line;
class Circle {
public:
	Point c;
	double r;
	Circle(Point c = Point(), double r = 0.0) :c(c), r(r) {}
};
pair<Point, Point>getC(Circle c, Line l) {
	Vector pr = project(l, c.c);
	Vector e = (l.p2 - l.p1) / abs(l.p2 - l.p1);
	double base = sqrt(c.r*c.r - norm(pr - c.c));
	return make_pair(pr + e*base, pr - e*base);
}
int main() {
	double r, n, m; cin >> r >> n >> m;
	Circle c({ 0., r }, r);
	double ans = 0;
	for (double j = 1; j <= n + m - 1; j++) {
		double i = ((2. * r) / n)*j, k = ((2.*r) / n)*(j - m);
		if (j - m <= 0) {
			Line l = { { -(1e7), i },{ 1e7, i } };
			auto p1 = getC(c, { { -(1e7),i } ,{ 1e7,i } });
			ans += sqrt(abs(p1.first.x - p1.second.x)*abs(p1.first.x - p1.second.x));
		}
		else if (j >= n - 1) {
			auto p2 = getC(c, { { -(1e7),k },{ 1e7,k } });
			ans += sqrt(abs(p2.first.x - p2.second.x)*abs(p2.first.x - p2.second.x));
		}
		else {
			auto p1 = getC(c, { { -(1e7),i } ,{ 1e7,i } }), p2 = getC(c, { { -(1e7),k },{ 1e7,k } });
			ans += max(sqrt(abs(p1.first.x - p1.second.x)*abs(p1.first.x - p1.second.x)),
				sqrt(abs(p2.first.x - p2.second.x)*abs(p2.first.x - p2.second.x)));
		}
	}
	printf("%.15lf\n", ans);
}

Submission Info

Judge Result