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){
    // TODO: 计算三角形T的面积
    //承接前面一道题，可以求点到直线的距离，并求线的长度，然后利用底高除2
    //x3,x2,x1 T.c.x y3 T.c.y
    double result,heigh, low,a,b;
    a  = T.b.y - T.a.y;
    b = T.b.x - T.a.x;
    heigh = abs((a*(T.c.x - T.b.x)- b*(T.c.y - T.b.y))/sqrt(a*a+b*b));
    low = sqrt((T.a.x - T.b.x)*(T.a.x - T.b.x)+(T.a.y - T.b.y)*(T.a.y - T.b.y));
    result = 0.5 *heigh *low;
    return result;    
}
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;
}