Submission #2233541

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

typedef long long   signed int LL;
typedef long long unsigned int LU;

#define incID(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define incII(i, l, r) for(int i = (l)    ; i <= (r); i++)
#define decID(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define decII(i, l, r) for(int i = (r)    ; i >= (l); i--)
#define  inc(i, n) incID(i, 0, n)
#define inc1(i, n) incII(i, 1, n)
#define  dec(i, n) decID(i, 0, n)
#define dec1(i, n) decII(i, 1, n)

#define inII(v, l, r) ((l) <= (v) && (v) <= (r))
#define inID(v, l, r) ((l) <= (v) && (v) <  (r))

#define PB push_back
#define EB emplace_back
#define MP make_pair
#define FI first
#define SE second
#define PQ priority_queue

#define  ALL(v)  v.begin(),  v.end()
#define RALL(v) v.rbegin(), v.rend()
#define  FOR(it, v) for(auto it =  v.begin(); it !=  v.end(); ++it)
#define RFOR(it, v) for(auto it = v.rbegin(); it != v.rend(); ++it)

template<typename T> bool   setmin(T & a, T b) { if(b <  a) { a = b; return true; } else { return false; } }
template<typename T> bool   setmax(T & a, T b) { if(b >  a) { a = b; return true; } else { return false; } }
template<typename T> bool setmineq(T & a, T b) { if(b <= a) { a = b; return true; } else { return false; } }
template<typename T> bool setmaxeq(T & a, T b) { if(b >= a) { a = b; return true; } else { return false; } }
template<typename T> T gcd(T a, T b) { return (b == 0 ? a : gcd(b, a % b)); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }

// ---- ----

typedef pair<double, double> Point;
Point p[3], I;

double distance_of_Point_to_Point(Point A, Point B) { // 点 A と点 B の距離
	return hypot(A.FI - B.FI, A.SE - B.SE);
}

double distance_of_Point_to_Line(Point P, Point A, Point B) { // 点 P と直線 AB の距離
	double a = B.SE - A.SE;
	double b = A.FI - B.FI;
	double c = A.SE * B.FI - A.FI * B.SE;
	// 直線 AB の方程式は ax + by + c = 0
	return abs(a * P.FI + b * P.SE + c) / hypot(a, b);
}

Point triangle_incenter(Point A, Point B, Point C) { // 三角形 ABC の内心の座標
	double a = distance_of_Point_to_Point(B, C);
	double b = distance_of_Point_to_Point(C, A);
	double c = distance_of_Point_to_Point(A, B);
	return MP(
		(a * A.FI + b * B.FI + c * C.FI) / (a + b + c), 
		(a * A.SE + b * B.SE + c * C.SE) / (a + b + c)
	);
}

double f(int a, int b) {
	double l = distance_of_Point_to_Point(p[a], p[b]);
	double h = distance_of_Point_to_Line(I, p[a], p[b]);
	return l / (2.0 + l / h);
}

int main() {
	inc(i, 3) { cin >> p[i].FI >> p[i].SE; }
	
	I = triangle_incenter(p[0], p[1], p[2]);
	
	double ans = 0.0;
	inc(i, 3) { setmax(ans, f(i, (i + 1) % 3)); }
	
	printf("%.12f\n", ans);
	
	return 0;
}

Submission Info

Judge Result