51nod 1298:圆与三角形（计算几何）

题目链接

判断圆和三角形是否相交   可以转化为   判断三条线段是否和圆相交

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<algorithm>
using namespace std;
typedef long long LL;

;

struct point
{
    double x,y;
    point operator -(const point& rhs)
    {
        point ret;
        ret.x=x-rhs.x;ret.y=y-rhs.y;
        return ret;
    }
    double operator *(const point& rhs)//“叉乘”
    {
        return x*rhs.y-y*rhs.x;
    }
    double operator ^(const point& rhs)//“点乘”
    {
        return x*rhs.x+y*rhs.y;
    }
}a[],o;
double r;

double dist(point a,point b)    //求点a,b的距离
{
    double x=a.x-b.x,y=a.y-b.y;
    return sqrt(x*x+y*y);
}
bool seg_cir(point a,point b)    //判断线段ab是否与圆o相交
{
    if(dist(a,o)<r-eps&&dist(b,o)<r-eps)
        return false;
    else if((r-dist(a,o))*(r-dist(b,o))<=eps)
        return true;
    else
    {
        ||((a-b)^(o-b))<)
            return false;
        double h=(a-o)*(b-o)/dist(a,b);
        h=fabs(h);
//        printf("%lf   %lf\n",(b-a)*(o-a),(a-b)*(o-b));
//        cout<<h<<"=========\n";
        return h<r+eps;
    }
}
bool ok()
{
    ;i<;i++)
        )%]))
            return true;
    return false;
}

int main()
{
    int T;cin>>T;
    while(T--)
    {
        cin>>o.x>>o.y>>r;
        ;i<;i++)
            cin>>a[i].x>>a[i].y;
        if(ok()) puts("Yes");
        else puts("NO");
    }
}