POJ 1556 计算几何基础

http://www.cnblogs.com/kuangbin/p/3189309.html#include<iostream>#include<iomanip>#include<queue>#include<algorithm>#include<cstdlib>#include<cstdio>#include<cstring>#include<cmath>using namespace std;const double eps=1e-8;int sgn(double x){    if (fabs(x)<eps) return 0;    if (x<0) return -1;    return 1;}struct Vector{    double x,y;    Vector() {};    Vector(double _x,double _y):x(_x),y(_y) {};    Vector operator+(const Vector& b) const    {        return Vector(x+b.x,y+b.y);    }    Vector operator-(const Vector& b) const    {        return Vector(x-b.x,y-b.y);    }    Vector operator*(double q) const    {        return Vector(x*q,y*q);    }};typedef Vector Point;inline double DotProduct(const Vector& a,const Vector& b){    return a.x*b.x+a.y*b.y;}inline double CrossProduct(const Vector& a,const Vector& b){    return a.x*b.y-a.y*b.x;}struct Segment{    Point s,e;    Segment() {};    Segment(Point _s,Point _e):s(_s),e(_e) {};};bool IsIntersected(Segment l1,Segment l2){    return max(l1.s.x,l1.e.x) >= min(l2.s.x,l2.e.x) &&           max(l2.s.x,l2.e.x) >= min(l1.s.x,l1.e.x) &&           max(l1.s.y,l1.e.y) >= min(l2.s.y,l2.e.y) &&           max(l2.s.y,l2.e.y) >= min(l1.s.y,l1.e.y) &&           sgn(CrossProduct(l2.s-l1.s,l1.e-l1.s))*sgn(CrossProduct(l2.e-l1.s,l1.e-l1.s)) <= 0 &&           sgn(CrossProduct(l1.s-l2.s,l2.e-l2.s))*sgn(CrossProduct(l1.e-l2.s,l2.e-l2.s)) <= 0;}double Dist(Point a,Point b){    return sqrt(DotProduct(b-a,b-a));}const int MAX=100;const double INF=1e20;Segment Seg[MAX];double Dis[MAX][MAX];int main(){    cin.sync_with_stdio(false);    cout<<fixed<<setprecision(2);    int n;    double x,y1,y2,y3,y4;    while (cin>>n&&n!=-1)    {        for (int i=1; i<=n; i++)        {            cin>>x>>y1>>y2>>y3>>y4;            Seg[2*i-1]=Segment(Point(x,y1),Point(x,y2));            Seg[2*i]=Segment(Point(x,y3),Point(x,y4));        }        for (int i=0; i<=4*n+1; i++)            for (int j=0; j<=4*n+1; j++)                if (i==j) Dis[i][j]=0;                else Dis[i][j]=INF;        for (int i=1; i<=4*n; i++)        {            int index=(i+3)/4;            bool flag=true;            Point temp;            if (i&1) temp=Seg[(i+1)/2].s;            else temp=Seg[(i+1)/2].e;            for (int j=1; j<index; j++)                if (IsIntersected(Seg[2*j-1],Segment(Point(0,5),temp))==false                        &&IsIntersected(Seg[2*j],Segment(Point(0,5),temp))==false)                    flag=false;            if (flag)                Dis[0][i]=Dis[i][0]=Dist(Point(0,5),temp);            flag=true;            for (int j=index+1; j<=n; j++)                if (IsIntersected(Seg[2*j-1],Segment(temp,Point(10,5)))==false                        &&IsIntersected(Seg[2*j],Segment(temp,Point(10,5)))==false)                    flag=false;            if (flag)                Dis[i][4*n+1]=Dis[4*n+1][i]=Dist(temp,Point(10,5));        }        for (int i=1; i<=4*n; i++)            for (int j=i+1; j<=4*n; j++)            {                int index1=(i+3)/4;                int index2=(j+3)/4;                bool flag=true;                Point p1,p2;                if (i&1) p1=Seg[(i+1)/2].s;                else p1=Seg[(i+1)/2].e;                if (j&1) p2=Seg[(j+1)/2].s;                else p2=Seg[(j+1)/2].e;                for (int k=index1+1;k<index2;k++)                    if (IsIntersected(Seg[2*k-1],Segment(p1,p2))==false                      &&IsIntersected(Seg[2*k],Segment(p1,p2))==false)                      flag=false;                if (flag) Dis[i][j]=Dis[j][i]=Dist(p1,p2);            }        bool flag=true;        for (int i=1;i<=n;i++)            if (IsIntersected(Seg[2*i-1],Segment(Point(0,5),Point(10,5)))==false              &&IsIntersected(Seg[2*i],Segment(Point(0,5),Point(10,5)))==false)              flag=false;        if (flag) Dis[0][4*n+1]=Dis[4*n+1][0]=10;        for (int k=0;k<=4*n+1;k++)            for (int i=0;i<=4*n+1;i++)                for (int j=0;j<=4*n+1;j++)                    if (Dis[i][k]+Dis[k][j]<Dis[i][j])                        Dis[i][j]=Dis[i][k]+Dis[k][j];        cout<<Dis[0][4*n+1]<<endl;    }    return 0;}