Cod sursa(job #2181554)
Utilizator | Nicolae Varticean Varticean | Data | 21 martie 2018 18:52:23 |
---|---|---|---|
Problema | Aria | Scor | 0 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.51 kb |
#include <bits/stdc++.h>
using namespace std;
ifstream in("aria.in");
ofstream out("aria.out");
int n;
struct point { int x,y; } a[100005];
double aria ()
{
double s =0;
for(int i=1; i<=n; i++)
s += ( a[i].x*a[i+1].y - a[i].y*a[i+1].x);
s /= 2;
return s;
}
int main()
{
ios::sync_with_stdio(0);
in >> n;
for(int i=1; i<=n; i++)
in >> a[i].x >> a[i].y ;
a[n+1] = a[1];
double A = aria();
out << fixed<< setprecision(5) << A;
return 0;
}