Cod sursa(job #2029211)
Utilizator | Gabriel Boroghina gabib97 | Data | 29 septembrie 2017 17:49:43 |
---|---|---|---|
Problema | Aria | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.46 kb |
#include <bits/stdc++.h>
#define N 100005
using namespace std;
int n, i;
long double s, x[N], y[N];
long double surf(int i, int j)
{
return (x[j] - x[1]) * (y[i] - y[1]) - (x[i] - x[1]) * (y[j] - y[1]);
}
int main()
{
freopen ("aria.in", "r", stdin);
freopen ("aria.out", "w", stdout);
scanf("%i", &n);
for (i = 1; i <= n; i++)
scanf("%Lf%Lf", &x[i], &y[i]);
for (i = 2; i <= n - 1; i++)
s += surf(i, i + 1);
printf("%Lf", fabs(s) / 2);
return 0;
}