intersecție segmente

#include <bits/stdc++.h>
#include <typeinfo>
#define NMAX 100001
#define x second
#define y first
using namespace std;
ifstream fin("is.in");
ofstream fout("is.out");
typedef pair<int, int>point;
struct event
{
    point p1,p2;
    int type;
    event() {};
    event(point p1,point p2, int type) : p1(p1), p2(p2),type(type) {};
};
int n,e, nrint;
event events[NMAX];
bool compare(event a, event b)
{
    return a.p1.x<b.p1.x;
}
set<point>s;
void hv_intersection()
{
    for (int i=0;i<e;++i)
    {
            event c = events[i];
            if (c.type==0)
                s.insert(c.p1);
            else if (c.type==1)
                s.erase(c.p2);
            else
            {
                for (typeof(s.begin()) it=s.lower_bound(make_pair(c.p1.y,-1));it!=s.end() && it->y<=c.p2.y; it++)
                                nrint++;
            }
        }
}
int main()
{
    int i;
    fin>>n;
    int p1x,p1y,p2x,p2y;
    for(i=0;i<n;i++)
    {
        fin>>p1x>>p1y>>p2x>>p2y;
        if(p1x==p2x)
        {
            events[e++]=event(make_pair(p1y,p1x),make_pair(p2y,p2x),2);
        }
        else
        {
            events[e++]=event(make_pair(p1y,p1x),make_pair(p2y,p2x),0);
            events[e++]=event(make_pair(p2y,p2x),make_pair(p1y,p1x),1);
        }
    }
    sort(events, events+e,compare);
    hv_intersection();
    fout<<nrint;
    return 0;
}