51Nod 1298 圆与三角形

#include <iostream>
#include <stdio.h>
#include <math.h>
using namespace std;

const double eps = 1e-8;
int cmp(double x)
{
    if (fabs(x) < eps) return 0;
    if (x > 0) return 1;
    return -1;
}

struct point
{
    double x, y;

    point() {}
    point(double a, double b) :x(a), y(b) {}

    void input() {
        scanf("%lf%lf", &x, &y);
    }
    //重载操作符
    friend point operator - (const point &a, const point &b) {
        return point(a.x - b.x, a.y - b.y);
    }

    double norm() {
        return sqrt(x*x + y*y);
    }
};

struct cicle
{
    point p;        //圆心
    double r;

    void input() {
        scanf("%lf%lf%lf", &p.x, &p.y, &r);
    }
};

double dot(const point &a, const point &b)
{
    return a.x*b.x + a.y*b.y;
}

double det(const point &a, const point &b)
{
    return a.x*b.y - a.y*b.x;
}

double dist(const point &a, const point &b)
{
    return (a - b).norm();
}

double dis_point_segment(const point p, const point s, const point t)
{
    if (cmp(dot(p - s, t - s))<0) return (p - s).norm();
    if (cmp(dot(p - t, s - t))<0) return (p - t).norm();
    return fabs(det(s - p, t - p) / dist(s, t));
}

bool cross(cicle o, point a, point b, point c)
{
    double d1, d2, d3;
    d1 = dist(o.p, a);
    d2 = dist(o.p, b);
    d3 = dist(o.p, c);
    //各点到圆心的距离
    if (d1<o.r && d2<o.r && d3<o.r)
        //都在圆内
        return false;
    if (dis_point_segment(o.p, a, b)>o.r 
        && dis_point_segment(o.p, a, c)>o.r 
        && dis_point_segment(o.p, b, c)>o.r)
        return false;
    return true;
}

int main()
{
    int T;
    scanf("%d", &T);
    while (T--) {
        cicle o;
        o.input();
        point a, b, c;
        a.input();
        b.input();
        c.input();
        if (cross(o, a, b, c))
            printf("Yes
");
        else
            printf("No
");
    }
    return 0;
}