poj2074 라인이 교차하는 시선 문제

#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 rdddd(x,y,z,w) scanf("%d%d%d%d",&x,&y,&z,&w)
#define rds(s) scanf("%s",s)
#define rep(i,n) for(int i=0;i<n;i++)
#define LL long long
const int N = 1000;
const int M=2000;
const int inf=0x3f3f3f3f;
const double eps=1e-8;
int MOD=1e9+7;
int cas=1;
int n,m,k,q;
struct Point{
    double x,y;
    Point(){}
    Point(double _x,double _y){
        x=_x;
        y=_y;
    }
    void print(){
        printf("x: %lf y: %lf
",x,y);
    }
};
struct Seg{
    Point s,e;
    Seg(){}
    Seg(Point _s,Point _e){
        s=_s;e=_e;
    }
    Seg(double a,double b,double c,double d){
        s.x=a;s.y=b;
        e.x=c;e.y=d;
    }
};
int sgn(double x) {return x<-eps?-1:x<eps?0:1;}
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);
}
Point inter(Seg a,Seg b){
    Point p1,p2,p3,p4;
    p1=a.s;p2=a.e;p3=b.s;p4=b.e;
    double a1=p1.y-p2.y;
    double b1=p2.x-p1.x;
    double c1=p1.x*p2.y-p2.x*p1.y;

    double a2=p3.y-p4.y;
    double b2=p4.x-p3.x;
    double c2=p3.x*p4.y-p4.x*p3.y;

    double x=(c2*b1-c1*b2)/(a1*b2-a2*b1);
    double y=(c2*a1-c1*a2)/(a2*b1-a1*b2);

    return Point(x,y);
}
Seg house,pro;
Seg seg;
double h1,h2;
double l,r;
struct node{
    double pos;
    int val;
    bool operator < (const node& o) const {
        return pos<o.pos;
    }
}c[N];
int main()
{
#ifndef ONLINE_JUDGE
  freopen("aaa","r",stdin);
#endif
    int T;
    double u,v,w;
    while(1){
        scanf("%lf%lf%lf",&u,&v,&w);
        if(u==0 && v==0 && w==0) break;
        house=Seg(u,w,v,w);
        h2=w;
        scanf("%lf%lf%lf",&u,&v,&w);
        pro=Seg(u,w,v,w);
        h1=w;
        l=u;r=v;
        rd(n);
        int cnt=0;
        for(int i=1;i<=n;i++){
            scanf("%lf%lf%lf",&u,&v,&w);
            if(w>h1 && w<h2){
                Point ret=inter(Seg(house.e,Point(u,w)),pro);
                double x1=ret.x;

                ret=inter(Seg(house.s,Point(v,w)),pro);
                double x2=ret.x;
                x2=min(x2,r);
                x1=max(x1,l);
                if(x1<=x2){
                    c[++cnt]=node{x1,-1};
                    c[++cnt]=node{x2,1};
                }
            }
        }
        sort(c+1,c+1+cnt);
        double ret=0;
        double pre=l;
        int num=0;
        for(int i=1;i<=cnt;i++){
                double p=c[i].pos;
                if(num>=0) ret=max(ret,p-pre);
                num+=c[i].val;
                pre=c[i].pos;
        }
        ret=max(ret,r-c[cnt].pos);
        if(sgn(ret)==0) puts("No View");
        else printf("%.2f
",ret);
    }

    return 0;
}