2 lygis | 1 pamoka| Trikampio plotas

#include <fstream>
#include <iomanip>
#include <cmath>
using namespace std;

const char duom[] = "Duomenys.txt";
const char rez[] = "Rezultatai.txt";

double krastines_ilgis(int x1, int y1, int x2, int y2) {
    return sqrt( pow(x1-x2, 2) + pow(y1-y2, 2) );
}

//Herono formulė
double plotas(int x1, int y1, int x2, int y2, int x3, int y3) {
    double a = krastines_ilgis(x1, y1, x2, y2);
    double b = krastines_ilgis(x1, y1, x3, y3);
    double c = krastines_ilgis(x2, y2, x3, y3);
    double p = (a+b+c)*0.5;// Pusperimetris
    return sqrt(p*(p-a)*(p-b)*(p-c));
}

int main() {
    int x1, y1, x2, y2, x3, y3;
    ifstream in(duom);
    ofstream out(rez);
    while( in >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 )
        out << fixed << setprecision(2) << plotas(x1, y1, x2, y2, x3, y3) << endl;
    return 0;
}