UVAlive 7366 Brocard（二分+计算几何）

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思路：二分Brocard angle设为rad，将两条边（AB，BC）按该角度旋转，求出两条边的交点P，判断CA与CP所成角度ang是否等于该角度，若rad>ang则rad应减小(r=mid)，即使得ang变大，否则rad应增大（l=mid），直到两者相等。

#include<cmath>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define debu
using namespace std;
const double pi=acos(-1.0);
struct Point
{
    double x,y;
    Point(double x=0,double y=0):x(x),y(y) {}
    void read()
    {
        scanf("%lf%lf",&x,&y);
    }
};
typedef Point Vector;
Vector operator + (Vector A,Vector B)
{
    return Vector(A.x+B.x,A.y+B.y);
}
Vector operator - (Point A,Point B)
{
    return Vector(A.x-B.x,A.y-B.y);
}
Vector operator * (Vector A,double p)
{
    return Vector(A.x*p,A.y*p);
}
Vector operator / (Vector A,double p)
{
    return Vector(A.x/p,A.y/p);
}
bool operator < (const Point& a,const Point& b)
{
    return a.x<b.x||(a.x==b.x&&a.y<b.y);
}
const double eps=1e-10;
int dcmp(double x)
{
    if(fabs(x)<eps) return 0;
    else return x<0?-1:1;
}
bool operator == (const Point& a ,const Point& b)
{
    return dcmp(a.x-b.x)==0&&dcmp(a.y-b.y)==0;
}
Point A,B,C,tmp;
double Dot(Vector A,Vector B)
{
    return A.x*B.x+A.y*B.y;
}
double Length(Vector A)
{
    return sqrt(Dot(A,A));
}
double Cross(Vector A,Vector B)
{
    return A.x*B.y-A.y*B.x;
}
double Angle(Vector A,Vector B)
{
    return acos(Dot(A,B)/Length(A)/Length(B));
}
Vector Rotate(Vector A,Vector B,double rad)
{
    Vector tmp=A-B;
    return Vector(B.x+tmp.x*cos(rad)-tmp.y*sin(rad),B.y+tmp.x*sin(rad)+tmp.y*cos(rad));
}
Point GetLineIntersection(Point P,Vector v,Point Q,Vector w)
{
    Vector u=P-Q;
    double t=Cross(w,u)/Cross(v,w);
    return P+v*t;
}
int check(double rad)
{
    Point b=Rotate(C,B,rad);
    Point a=Rotate(B,A,rad);
    tmp=GetLineIntersection(B,b-B,A,a-A);
    double ang=Angle(tmp-C,A-C);
    //cout<<rad<<" "<<a.x<<" "<<a.y<<" "<<b.x<<" "<<b.y<<" "<<tmp.x<<" "<<tmp.y<<" "<<ang<<endl;
    return rad-ang>eps;
}
int main()
{
#ifdef debug
    freopen("in.in","r",stdin);
#endif // debug
    int t;
    scanf("%d",&t);
    while(t--)
    {
        int cas=0;
        double ax,ay,bx,by,cx,cy;
        scanf("%d",&cas);
        A.read(),B.read(),C.read();
        double ang1=Angle(C-B,A-B),ang2=Angle(B-A,C-A),ang3=Angle(A-C,B-C);
        double l=0.0,r=min(ang1,min(ang2,min(pi/6,ang3)));
        while(r-l>eps)
        {
            double mid=(l+r)/2;
            if(check(mid)) r=mid;
            else l=mid;
        }
        printf("%d %.5f %.5f\n",cas,tmp.x,tmp.y);
    }
    return 0;
}

UVAlive 7366 Brocard（二分+计算几何）

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原文地址：http://blog.csdn.net/wang2147483647/article/details/52269459