poj1556 判断线段相交+最短路

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<string>
#include<stdlib.h>
#include<cmath>
#include<queue>
#include<algorithm>
using namespace std;
#define rd(x) scanf("%d",&x)
#define rdd(x,y) scanf("%d%d",&x,&y)
#define rddd(x,y,z) scanf("%d%d%d",&x,&y,&z)
#define rds(s) scanf("%s",s)
#define rep(i,n) for(int i=0;i<n;i++)
#define LL long long
const int N = 100;
const int M=5e5+10;
const int inf=1e9;
const double eps=1e-5;
const int MOD=1e9+7;
int n,m;
struct Point{
double x,y;
Point(){

}
Point(double _x,double _y){
x=_x;y=_y;
}
};
Point p1,p2,p3,p4;
struct Seg{
Point s,e;
Seg(){}
Seg(Point _s,Point _e){
s=_s;
e=_e;
}
Seg(double x,double y,double xx,double yy){
s.x=x;s.y=y;
e.x=xx;e.y=yy;
}
};
double cross(Point a,Point b,Point c){
return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}
double dist(Point a,Point b){
return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}
int sgn(double x){ return x<-eps?-1:x<eps?0:1;}
void solve( ){

}

int pn,ps;
int tot;
Seg seg[500];
Point point[500];
int head[500];
struct Edge{
int to,nxt;
double w;
}edge[500*500];
void addEdge(int u,int v,double w){
edge[tot].to=v;
edge[tot].nxt=head[u];
edge[tot].w=w;
head[u]=tot++;
}
bool jiao(Point a,Point b){

for(int i=0;i<ps;i++){
if(   seg[i].s.x<b.x && seg[i].s.x>a.x  &&
sgn(cross(a,b,seg[i].s))*sgn(cross(a,b,seg[i].e))<=0
) return true;
}
return false;
}
bool vis[500];
double dis[500];
queue<int> q;
int main()
{
#ifndef ONLINE_JUDGE
freopen("aaa","r",stdin);
#endif
int T;
while(true){
rd(n);
if(n==-1) break;
ps=0;
pn=0;
point[pn++]=Point(0,5);
for(int i=1;i<=n;i++){
double u,v1,v2,v3,v4;
scanf("%lf%lf%lf%lf%lf",&u,&v1,&v2,&v3,&v4);
seg[ps++]=Seg(u,0,u,v1);
seg[ps++]=Seg(u,v2,u,v3);
seg[ps++]=Seg(u,v4,u,10);

point[pn++]=Point(u,v1);
point[pn++]=Point(u,v2);
point[pn++]=Point(u,v3);
point[pn++]=Point(u,v4);

}
point[pn++]=Point(10,5);

tot=0;
memset(head,-1,sizeof head);

for(int i=0;i<pn;i++)
for(int j=i+1;j<pn;j++) if(!jiao(point[i],point[j])){
addEdge(i,j,dist(point[i],point[j]));
}

for(int i=0;i<pn;i++){
dis[i]=inf;
vis[i]=0;
}
while(!q.empty()) q.pop();
vis[0]=1;
dis[0]=0;
q.push(0);
while(!q.empty()){
int u=q.front();q.pop();
vis[u]=0;
for(int k=head[u];~k;k=edge[k].nxt){
int v=edge[k].to;
double w=edge[k].w;
if(dis[v]>dis[u]+w){
dis[v]=dis[u]+w;
if(!vis[v]){
vis[v]=1;
q.push(v);
}
}
}
}
printf("%.2f\n",dis[pn-1]);
}

return 0;
}