ACM常见问题之【三角形的外心】

该点到三角形三个顶点距离相同，即三角形的外心。

#include<bits/stdc++.h>
using namespace std;
int main()
{
    
    
    double x1, x2, x3, y1, y2, y3;
    cin>>x1>>y1>>x2>>y2>>x3>>y3;
    double A1 = 2 * (x2 - x1),
    B1 = 2 * (y2 - y1),
    C1 = x2 * x2 - x1 * x1 - y1 * y1 + y2 *y2,
    A2 = 2 * (x3 - x2),
    B2 = 2 * (y3 - y2),
    C2 = x3 * x3 - x2 * x2 - y2 * y2  + y3 * y3;
    double x,y;
    x=((C1*B2)-(C2*B1))/((A1*B2)-(A2*B1));
    y=((A1*C2)-(A2*C1))/((A1*B2)-(A2*B1));
    printf("%.3lf %.3lf\n",x,y);
    return 0;
}