Cod sursa(job #2432843)
Utilizator | Teodor Matei Shay | Data | 25 iunie 2019 11:58:05 |
---|---|---|---|
Problema | Aria | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva educationala | Marime | 0.51 kb |
#include <fstream>
#include <assert.h>
#include <iomanip>
int main() {
std::ifstream cin("aria.in");
std::ofstream cout("aria.out");
std::ios::sync_with_stdio(false);
int n;
long double sum = 0;
cin >> n;
assert(1 <= n && n <= 100000);
long double x[n], y[n];
for (int i = 0 ; i < n ; ++i) {
cin >> x[i] >> y[i];
}
x[n] = x[0];
y[n] = y[0];
for (int i = 0 ; i < n ; ++i) {
sum += x[i] * y[i + 1] - x[i + 1] * y[i];
}
cout << std::fixed << std::setprecision(7) << sum / 2.0 << '\n';
return 0;
}