Submission #110890

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Source Code Expand

#define _CRT_SECURE_NO_WARNINGS
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <cctype>
#include <list>
#include <cassert>
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
#if defined(_MSC_VER) || __cplusplus > 199711L
#define aut(r,v) auto r = (v)
#else
#define aut(r,v) typeof(v) r = (v)
#endif
#define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it)
#define all(o) (o).begin(), (o).end()
#define pb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))
#define mset(m,v) memset(m,v,sizeof(m))
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
#define EPS 1e-9
using namespace std;
typedef vector<int> vi; typedef pair<int,int> pii; typedef vector<pair<int,int> > vpii;
typedef long long ll; typedef vector<long long> vl; typedef pair<long long,long long> pll; typedef vector<pair<long long,long long> > vpll;
typedef vector<string> vs; typedef long double ld;

struct P {
	typedef int T; typedef ll T2;	//T2は{a*b | a:T, b:T}を含むタイプ
	T x, y;
	P(T x_, T y_): x(x_), y(y_) {}
	P(): x(0), y(0) {}
};
inline bool operator==(const P& a, const P& b) { return a.x == b.x && a.y == b.y; }
inline bool operator<(const P& a, const P& b) { return a.x < b.x || (a.x == b.x && a.y < b.y); }
inline P operator+(const P& a, const P& b) { return P(a.x+b.x, a.y+b.y); }
inline P operator-(const P& a, const P& b) { return P(a.x-b.x, a.y-b.y); }
inline P operator-=(P& a, const P& b) { a.x -= b.x, a.y -= b.y ; return a; }
inline P::T2 cross(const P& a, const P& b) { return (P::T2)a.x*b.y - (P::T2)a.y*b.x; }
inline P::T2 dot(const P& a, const P& b) { return (P::T2)a.x*b.x + (P::T2)a.y*b.y; }
inline P::T2 norm(const P& a) { return (P::T2)a.x*a.x + (P::T2)a.y*a.y; }
ostream& operator<<(ostream& out, const P& x) { out << "(" << x.x << ", " << x.y << ")"; return out; }

inline int ccw(const P& a, const P& b, const P& c) {
	int ax = b.x - a.x, ay = b.y - a.y, bx = c.x - a.x, by = c.y - a.y;
	P::T2 t = (P::T2)ax*by - (P::T2)ay*bx;
	if (t > 0) return 1;
	if (t < 0) return -1;
	if((P::T2)ax*bx + (P::T2)ay*by < 0) return +2;
	if((P::T2)ax*ax + (P::T2)ay*ay < (P::T2)bx*bx + (P::T2)by*by) return -2;
	return 0;
}
P::T2 area(const vector<P>& o) {
  P::T2 A = 0;
  for (int i = 0; i < o.size(); ++i) 
    A += cross(o[i], o[(i+1)%o.size()]);
  return abs(A);
}

int main() {
	vector<P> p;
	rep(i, 3) {
		int x, y;
		cin >> x >> y;
		p.pb(P(x,y));
	}
	printf("%.10f\n", area(p)/2.);
	return 0;
}

Submission Info

Judge Result