poj-1556-The Doors-dij+线段相交

#include<iostream>
#include<string.h>
#include<algorithm>
#include<stdio.h>
#include<math.h>
using namespace std;
#define maxn 200000
#define eps 0.00001
#define zero(x) ((fabs(x)<eps)?0:x)
#define maxx 9999999
struct point
{
    double x;
    double y;
} p[20000],pp;
struct line
{
    point a;
    point b;
} l[20000];
int lnum;
double xmult(point p1,point p2,point p0)
{
    return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);
}
bool opposite_side(point u1,point u2,point v1,point v2)
{
    return xmult(v1,u1,u2)*xmult(v2,u1,u2)<-eps;
}
bool jiao(point u1,point u2,point v1,point v2)
{
    return opposite_side(u1,u2,v1,v2)&&opposite_side(v1,v2,u1,u2);
}
double dis(point a,point b)
{
    return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}
struct list
{
    int u;
    int v;
    double w;
    int next;
} edge[maxn];
int head[maxn];
int num;
void add(int u,int v,double w)
{
    edge[num].u=u;
    edge[num].v=v;
    edge[num].w=w;
    edge[num].next=head[u];
    head[u]=num++;
}
int pan(point a,point b)
{
    for(int i=0;i<lnum;i++)
    {
        if(jiao(l[i].a,l[i].b,a,b))return 1;
    }
    return 0;
}
void dij(int y)
{
    double d[1100];
    int vis[1100];
    int i;
    for(i=0;i<=y;i++)d[i]=maxx;
    memset(vis,0,sizeof(vis));
    d[0]=0;
    while(1)
    {
        int ip;
        int minn=maxx;
        for(i=0;i<=y;i++)
        {
            if(vis[i])continue;
            if(d[i]<minn){minn=d[i];ip=i;}
        }
        if(minn==maxx)break;
        vis[ip]=1;
        for(i=head[ip];i!=-1;i=edge[i].next)
        {
            int v=edge[i].v;
            if(vis[v])continue;
            d[v]=min(d[v],d[ip]+edge[i].w);
        }
    }
    printf("%.2f\n",d[y]);
}
int main()
{
    int n,i,j,k;
    double x;
    while(~scanf("%d",&n))
    {
        memset(head,-1,sizeof(head));
        if(n==-1)break;
        p[0].x=0;
        p[0].y=5;
        num=0;
        lnum=0;
        for(i=1; i<=n; i++)
        {
            cin>>x;
            pp.x=x;
            pp.y=0;
            l[lnum].a=pp;
            for(k=1; k<=4; k++)
            {
                cin>>p[(i-1)*4+k].y;
                p[(i-1)*4+k].x=x;
                for(j=0; j<=(i-1)*4; j++)
                {
                    if(!pan(p[j],p[(i-1)*4+k]))add(j,(i-1)*4+k,dis(p[j],p[(i-1)*4+k]));
                }
            }
            pp.y=p[i*4-3].y;
            l[lnum++].b=pp;
            pp.y=p[i*4-2].y;
            l[lnum].a=pp;
            pp.y=p[i*4-1].y;
            l[lnum++].b=pp;
            pp.y=p[i*4].y;
            l[lnum].a=pp;
            pp.y=10;
            l[lnum++].b=pp;
        }
        p[n*4+1].x=10;
        p[n*4+1].y=5;
        for(j=0; j<=n*4; j++)
        {
            if(!pan(p[j],p[n*4+1]))add(j,n*4+1,dis(p[j],p[n*4+1]));
        }
        dij(n*4+1);
    }
    return 0;
}