Pagini recente » Cod sursa (job #1876491) | Rezultatele filtrării | Borderou de evaluare (job #1493353) | Cod sursa (job #1789374) | Cod sursa (job #2122555)
#include <bits/stdc++.h>
#define NMAX 100001
using namespace std;
ifstream fin("aria.in");
ofstream fout("aria.out");
struct point{
double x, y;
};
int n;
point O, A, B;
double aria;
double det(point A, point B, point C) {
return (A.x * B.y + B.x * C.y + C.x * A.y - B.y * C.x - C.y * A.x - A.y * B.x) / 2;
}
int main()
{
fin >> n;
O.x = O.y = 0;
fin >> A.x >> A.y;
for(int i = 2; i <= n; i++) {
fin >> B.x >> B.y;
aria += det(O, A, B);
A = B;
}
fout << fixed;
fout << setprecision(5) << aria << '\n';
return 0;
}