【洛谷p1766】液体滴落

这个题……我被坑了大半天qwq，这模拟真恶心

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
int n,tail,ans,t;
struct in
{
    double gx,gy,dx,dy;
}ter[10010];
bool cmp(in a,in b)
{
    return a.dy>b.dy;
}
bool bj(int a,int b)//a为当前线段，b为可能的答案 
{
    return min(ter[b].gx,ter[b].dx)<ter[a].dx&&max(ter[b].gx,ter[b].dx)>ter[a].dx;
}
bool dow(int i,int j,int x)//i靠下的线段，j为靠上的线段 
{
    if(j==0)
        return 1;
    double h1,h2;
    h1=(double)(ter[i].gy-ter[i].dy)/(ter[i].gx-ter[i].dx)*x+ter[i].gy-(ter[i].gy-ter[i].dy)/(ter[i].gx-ter[i].dx)*ter[i].gx;
    h2=(double)(ter[j].gy-ter[j].dy)/(ter[j].gx-ter[j].dx)*x+ter[j].gy-(ter[j].gy-ter[j].dy)/(ter[j].gx-ter[j].dx)*ter[j].gx;
    if(h1<h2)
        return 1;
    return 0;
}
int main()
{
    scanf("%d%d",&n,&ans);
    for(int i=1;i<=n;i++)
    {
        scanf("%lf%lf%lf%lf",&ter[i].gx,&ter[i].gy,&ter[i].dx,&ter[i].dy);
        if(ter[i].gy<ter[i].dy)
            swap(ter[i].gy,ter[i].dy),swap(ter[i].gx,ter[i].dx);
    }
    tail=0;
    sort(ter+1,ter+1+n,cmp);
    //for(int i=1;i<=n;i++)
    //    cout<<ter[i].gx<<' '<<ter[i].gy<<' '<<ter[i].dx<<' '<<ter[i].dy<<endl;
    ter[0].dx=ans;
    while(tail<=n)
    {
        t=-1;
        for(int j=tail+1;j<=n;j++)
            if(bj(tail,j))
                if(dow(j,tail,ter[tail].dx))
                    if(t==-1||dow(t,j,ter[tail].dx))
                        t=j;
        if(t==-1)
            break;
        tail=t;
    }
    printf("%d",(int)ter[tail].dx);
}