题解 | 三角形面积

#include <bits/stdc++.h>
using namespace std;

struct point{
    double x,y;
    point(double A,double B){
        x=A,y=B;
    }
    point() = default;
};

struct triangle{
    point a,b,c;
    triangle(point A,point B,point C){
        a=A,b=B,c=C;
    }
    triangle() = default;
};

double getArea(triangle T)
{
    point v1,v2;
    v1.x=T.b.x-T.a.x;
    v1.y=T.b.y-T.a.y;
    v2.x=T.c.x-T.a.x;
    v2.y=T.c.y-T.a.y;
    double s=abs(v1.x*v2.y-v1.y*v2.x)/2;
    return s;
}

































































































































































































int main(){
    int x, y;
    cin >> x >> y;
    point a(x, y);
    cin >> x >> y;
    point b(x, y);
    cin >> x >> y;
    point c(x, y);
    triangle T(a, b, c);
    cout << fixed << setprecision(2) << getArea(T) << endl;
    return 0;
}