sicily 1741

#include "iostream"#include "iomanip"using namespace std;struct Info{    int X;    int Y;};double area(double a, double b, double c, double d){    double differX = c - a;    double differY;    double mult1 = 0, mult2 = 0;    if (b > d)    {        mult1 = differX * d;        differY = b - d;    }    else    {        mult1 = differX * b;        differY = d - b;    }     mult2 = differX * differY / 2;     return (mult1 + mult2);}int main(){    int T;    cin >> T;    while (T--)    {        int N;        cin >> N;        Info *a = new Info[N];        for (int i = 0; i < N; i++)            cin >> a[i].X >> a[i].Y;        double areaSum = 0;        for (int i = 0; i < N-1; i++)            areaSum += area(a[i].X, a[i].Y, a[i+1].X, a[i+1].Y);       /* cout.setf(ios_base::showbase);        cout.setf(ios_base::fixed);        cout.setf(ios_base::floatfield);        cout.setf(ios_base::showpoint);        cout.precision(2);        cout << setiosflags(ios::showpoint) << areaSum << endl;*/        cout << fixed << setprecision(1) << areaSum << endl;    }}