题解 | 三角形面积|海伦公式

#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 len(point a,point b){
    return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}

double getArea(triangle T) {
    // TODO: 计算三角形T的面积
    double p = (len(T.a,T.b)+len(T.a,T.c)+len(T.b,T.c))/2;
    return sqrt(p*(p-len(T.a,T.b))*(p-len(T.a,T.c))*(p-len(T.b,T.c)));
    }


































































































































































































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;
}