Cod sursa(job #1135884)

Utilizator vladrochianVlad Rochian vladrochian Data 8 martie 2014 15:20:59
Problema Aria Scor 0
Compilator cpp Status done
Runda Arhiva educationala Marime 0.35 kb
Raporteaza aceasta sursa 
#include <fstream>
#include <iomanip>
using namespace std;
int n,a,x[100001],y[100001],i;
ifstream fin("aria.in");
ofstream fout("aria.out");
int main()
{
	fin>>n;
	for(i=0;i<n;++i)
		fin>>x[i]>>y[i];
	x[n]=x[0];
	y[n]=y[0];
	for(i=0;i<n;++i)
		a+=x[i]*y[i+1]-x[i+1]*y[i];
	fout<<setprecision(6)<<fixed<<(double)a/2<<"\n";
	return 0;
}