HDU 4454 Stealing a Cake --枚举

题意： 给一个点，一个圆，一个矩形， 求一条折线，从点出发，到圆，再到矩形的最短距离。

解法： 因为答案要求输出两位小数即可，精确度要求不是很高，于是可以试着爆一发，暴力角度得到圆上的点，然后求个距离，求点到矩形的距离就是求点到四边的距离然后求个最小值，然后总的取个最小值即可。

代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#define Mod 1000000007
#define pi acos(-1.0)
#define eps 1e-8
using namespace std;
#define N 1000107

typedef struct Point
{
    double x,y;
    Point(double x=0,double y=0):x(x),y(y){}
    Point(){}
}Vector;

int sgn(double x)
{
    if(x > eps) return 1;
    if(x < -eps) return -1;
    return 0;
}
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); }
bool operator == (const Point& a,const Point& b) { return (sgn(a.x-b.x) == 0 && sgn(a.y-b.y) == 0); }
double Dot(Vector A,Vector B) { return A.x*B.x + A.y*B.y; }
double Cross(Vector A,Vector B) { return A.x*B.y - A.y*B.x; }
double Length(Vector A) { return sqrt(Dot(A,A)); }
double PtoSeg(Point P,Point A,Point B)
{
    if(A == B) return Length(P-A);
    Vector V1 = B-A;
    Vector V2 = P-A;
    Vector V3 = P-B;
    if(sgn(Dot(V1,V2)) < 0) return Length(V2);
    else if(sgn(Dot(V1,V3)) > 0) return Length(V3);
    else return fabs(Cross(V1,V2))/Length(V1);
}

int main()
{
    double X,Y;
    double Cx,Cy,R;
    double x1,y1,x2,y2;
    while(scanf("%lf%lf",&X,&Y)!=EOF)
    {
        if(sgn(X) == 0 && sgn(Y) == 0) break;
        scanf("%lf%lf%lf",&Cx,&Cy,&R);
        scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
        Point A = Point(x1,y1);
        Point B = Point(x1,y2);
        Point C = Point(x2,y1);
        Point D = Point(x2,y2);
        double delta = 2.0*pi*0.0001;
        double Min = Mod;
        for(int Angle=1;Angle<=10000;Angle++)
        {
            double ang = delta*Angle;
            double nx = Cx + R*cos(ang);
            double ny = Cy + R*sin(ang);
            double D1 = PtoSeg(Point(nx,ny),A,B);
            double D2 = PtoSeg(Point(nx,ny),A,C);
            double D3 = PtoSeg(Point(nx,ny),B,D);
            double D4 = PtoSeg(Point(nx,ny),C,D);
            double Dis = sqrt((nx-X)*(nx-X)+(ny-Y)*(ny-Y))+min(min(min(D1,D2),D3),D4);
            Min = min(Dis,Min);
        }
        printf("%.2f\n",Min);
    }
    return 0;
}