点到线段的最大最小距离

点到线段的最大最小距离

//点到线段的最大最小距离
//注意判断垂足是否在线段上
double Distance(Point a,Point b,Point c) {
    if(a.x == b.x) {
        if(c.y >= min(a.y,b.y) && c.y <= max(a.y,b.y))  
            return fabs(a.x - c.x);
        return min(Dis(a,c),Dis(b,c));
    }
    double k = (a.y - b.y) / (a.x - b.x);
    double tempb = a.y - k * a.x;
    Point p;
    p.x = (c.x + k * c.y - k * tempb) / (k * k + 1);
    p.y = k * p.x + tempb;
    if(p.x >= min(a.x,b.x) && p.x <= max(a.x,b.x))  
        return Dis(p,c);
    return min(Dis(a,c),Dis(b,c));
}