poj 1066 Treasure Hunt 计算几何计数
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题目地址:poj1066
只能从中点进入--姑且理解为要进入另一个区域,一定只能“边相邻”。
关于穿过最小边的方案--把目标点和每一个边上的点连线,相交,交点数+1 就是可能的结果之一。
额,最小性的只是感觉上的,还没有严格的证明,以后想到了再补充吧。
代码:
#include<iostream>#include<cmath>#include<cstdio>#include<algorithm>#include<cstring>#include<map>#include<vector>const double eps=1e-8;using namespace std;struct Point{ double x; double y; Point(double x=0,double y=0):x(x),y(y){} void operator<<(Point &A) {cout<<A.x<<' '<<A.y<<endl;}};int dcmp(double x) {return (x>eps)-(x<-eps); }typedef Point Vector;Vector operator +(Vector A,Vector B) { return Vector(A.x+B.x,A.y+B.y);}Vector operator -(Vector A,Vector 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);}// ps coutostream &operator<<(ostream & out,Point & P) { out<<P.x<<' '<<P.y<<endl; return out;}bool operator< (const Point &A,const Point &B) { return A.x<B.x||(A.x==B.x&&A.y<B.y); }bool operator== ( const Point &A,const Point &B) { return dcmp(A.x-B.x)==0&&dcmp(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-B.x*A.y; }double Length(Vector A) { return sqrt(Dot(A, A));}double Angle(Vector A,Vector B) {return acos(Dot(A,B)/Length(A)/Length(B));}double Area2(Point A,Point B,Point C ) {return Cross(B-A, C-A);}Vector Rotate(Vector A,double rad) { return Vector(A.x*cos(rad)-A.y*sin(rad),A.x*sin(rad)+A.y*cos(rad));}Vector Normal(Vector A) {double L=Length(A);return Vector(-A.y/L,A.x/L);}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; }double DistanceToLine(Point P,Point A,Point B){ Vector v1=P-A; Vector v2=B-A; return fabs(Cross(v1,v2))/Length(v2); }double DistanceToSegment(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(dcmp(Dot(v1,v2))==-1) return Length(v2); else if(Dot(v1,v3)>0) return Length(v3); else return DistanceToLine(P, A, B); }Point GetLineProjection(Point P,Point A,Point B){ Vector v=B-A; Vector v1=P-A; double t=Dot(v,v1)/Dot(v,v); return A+v*t;}bool SegmentProperIntersection(Point a1,Point a2,Point b1,Point b2){ double c1=Cross(b1-a1, a2-a1); double c2=Cross(b2-a1, a2-a1); double c3=Cross(a1-b1, b2-b1); double c4=Cross(a2-b1, b2-b1); return dcmp(c1)*dcmp(c2)<0&&dcmp(c3)*dcmp(c4)<0 ; }bool OnSegment(Point P,Point A,Point B){ return dcmp(Cross(P-A, P-B))==0&&dcmp(Dot(P-A,P-B))<=0;}double PolygonArea(Point *p,int n){ double area=0; for(int i=1;i<n-1;i++) { area+=Cross(p[i]-p[0], p[i+1]-p[0]); } return area/2; }Point read_point(){ Point P; scanf("%lf%lf",&P.x,&P.y); return P;}double min(double x,double y){ return x<y?x:y; }double max(double x,double y){ return x>y?x:y; }Point p[100];Point a[35],b[35];int main(){ int n; cin>>n; for(int i=0;i<n;i++) { a[i]=read_point(); b[i]=read_point(); } int cnt=0; for(int i=0;i<n;i++) { p[cnt++]=a[i]; p[cnt++]=b[i]; } p[cnt++]=Point(0,0); p[cnt++]=Point(0,100); p[cnt++]=Point(100,0); p[cnt++]=Point(100,100); Point target; target=read_point(); int ans; bool first=1; for(int i=0;i<cnt;i++) { int count=0; for(int j=0;j<n;j++) { if(SegmentProperIntersection(p[i], target, a[j], b[j])) count++; } if(first) ans=count; if(first) first=0; else { ans=min(ans,count); } } printf("Number of doors = %d\n",ans+1); }
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