Submission #1001315

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Source Code Expand

#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(n);++i)
#define ALL(A) A.begin(), A.end()
#define EPS (1e-12)

using namespace std;

typedef long long ll;
typedef pair<int, int> P;
typedef pair<double, int> DI;

double calc_dist(int x1, int y1, int x2, int y2){
	double res = (sqrt)((x1 - x2) * (x1 - x2) + (y1 - y2)*(y1 - y2));
	return res;
}

double calc_area(double a, double b, double c){
	double s = (a + b + c) / 2.;
	double res = sqrt(s * (s - a) * (s - b) * (s - c));

	return res;
}

double calc_cos(double a, double b, double c){
	double res = (-a*a + b*b + c*c) / 2. / b / c;
	return res;
}

double calc_sin(double a, double b, double c, int i){
	double s = calc_area(a, b, c);
	double res = 2.* s;
	switch(i){
		case 0: res /= b; res /= c; break;
		case 1: res /= c; res /= a; break;
		case 2: res /= a; res /= b; break;
	} // end switch;

	return res;
}

double calc_half_cos(double cos){
	return sqrt((1. + cos) / 2.);
}

double calc_half_sin(double cos){
	return sqrt((1. - cos) / 2.);
}

double calc_half_inv_tan(double cos){
	return sqrt((1. + cos) / (1. - cos));
}

double calc_term_plus(double cos){
	return sqrt(1. + cos);
}

double calc_term_minus(double cos){
	return sqrt(1. - cos);
}

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	int x[3] = {0};
	int y[3] = {0};
	rep (i, 3) cin >> x[i] >> y[i];
	DI l[3];
	rep (i, 3){
		l[i].first = calc_dist(x[i], y[i], x[(i+1)%3], y[(i+1)%3]);
		l[i].second = i;
	} // end rep
	sort(l, l+3);

	double s = calc_area(l[0].first, l[1].first, l[2].first);
	double a = l[2].first;
	double b = l[1].first;
	double c = l[0].first;

	double min_r = 0.;
	double max_r = 2.* s / (a + b + c);

	double min_cos = calc_cos(l[0].first, l[1].first, l[2].first);
	double half_min_cos = calc_half_cos(min_cos); 
	double half_min_sin = calc_half_sin(min_cos);

	double mid_cos = calc_cos(l[1].first, l[2].first, l[0].first);
	double half_mid_cos = calc_half_cos(mid_cos);
	double half_mid_sin = calc_half_sin(mid_cos);


	double min_term_plus = calc_term_plus(min_cos);
	double min_term_minus = calc_term_minus(min_cos);
	double mid_term_plus = calc_term_plus(mid_cos);
	double mid_term_minus = calc_term_minus(mid_cos);

	double res = 0.;
	while(abs(max_r - min_r) > EPS){
		double mid_r = (min_r + max_r) / 2.;
//		cerr << "mid_r: " << mid_r << endl;
	
		if (mid_r * (min_term_plus*mid_term_minus + mid_term_plus*min_term_minus + 2.*min_term_minus*mid_term_minus) 
			< a*min_term_minus*mid_term_minus + EPS){
			res = max(res, mid_r);
			min_r = mid_r;
		}else{
			max_r = mid_r;
		} // end if
	} // end while

	printf("%.12lf\n", res);

	return 0;
}

Submission Info

Judge Result