[Gym - 100517K] Kingdom Division 2 二分

大致题意：

　　给出一个凸包，以及凸包内的两个点p1,p2，求有多少条经过凸包顶点的直线能够将凸包分割为两部分，且给出的两点分别属于不同的部分

　　

　　枚举凸包的顶点，二分求出p1,p2线段左边的最大坐标L以及右边的最小坐标R，则答案为R-L-1的累加和除以2

　　注意文件输入，输出

　　　

 #include<cstdio>
 #include<iostream>
 #include<cstring>
 #include<algorithm>
 #include<queue>
 #include<set>
 #include<map>
 #include<stack>
 #include<time.h>
 #include<cstdlib>
 #include<cmath>
 #include<list>
 using namespace std;
 #define MAXN 100100
 #define eps 1e-9
 #define For(i,a,b) for(int i=a;i<=b;i++)
 #define Fore(i,a,b) for(int i=a;i>=b;i--)
 #define lson l,mid,rt<<1
 #define rson mid+1,r,rt<<1|1
 #define mkp make_pair
 #define pb push_back
 #define cr clear()
 #define sz size()
 #define met(a,b) memset(a,b,sizeof(a))
 #define iossy ios::sync_with_stdio(false)
 #define fre freopen
 #define pi acos(-1.0)
 #define inf 1e6+7
 #define Vector Point
 const int Mod=1e9+;
 typedef unsigned long long ull;
 typedef long long ll;
 int dcmp(double x){
     if(fabs(x)<=eps) return ;
     return x<?-:;
 }
 struct Point{
     double x,y;
     int id;
     Point(double x=,double y=):x(x),y(y) {}
     bool operator < (const Point &a)const{
         if(x==a.x) return y<a.y;
         return x<a.x;
     }
     Point operator - (const Point &a)const{
         return Point(x-a.x,y-a.y);
     }
     Point operator + (const Point &a)const{
         return Point(x+a.x,y+a.y);
     }
     Point operator * (const double &a)const{
         return Point(x*a,y*a);
     }
     Point operator / (const double &a)const{
         return Point(x/a,y/a);
     }
     void read(){
         scanf("%lf%lf",&x,&y);
     }
     void out(){
         cout<<"debug: "<<x<<" "<<y<<endl;
     }
     bool operator == (const Point &a)const{
         return dcmp(x-a.x)== && dcmp(y-a.y)==;
     }
 };
 double Dot(Vector a,Vector b) {
     return a.x*b.x+a.y*b.y;
 }
 double dis(Vector a) {
     return sqrt(Dot(a,a));
 }
 double Cross(Point a,Point b){
     return a.x*b.y-a.y*b.x;
 }
 int n;
 Point p[];
 int ls,rs;
 int chk1(Point p1,Point p2,int pos){
     int l=pos+,r=pos+n-;
     while(l<r){
         int mid=l+r>>;
         if(dcmp(Cross(p[mid]-p[pos],p1-p[pos]))<= && dcmp(Cross(p[mid]-p[pos],p2-p[pos])<=)) r=mid;
         else l=mid+;
     }
     return l;
 }
 int chk2(Point p1,Point p2,int pos){
     int l=pos+,r=pos-+n;
     while(l<r){
         int mid=l+r+>>;
         if(dcmp(Cross(p[mid]-p[pos],p1-p[pos]))>= && dcmp(Cross(p[mid]-p[pos],p2-p[pos]))>=) l=mid;
         else r=mid-;
     }
     return l;
 }
 Point p1,p2;
 void solve(){
     For(i,,n) p[i].read();
     p1.read();p2.read();
     ll ans=;
     For(i,,n) p[i+n]=p[i];
     For(i,,n){
         ls=chk1(p1,p2,i);
         rs=chk2(p1,p2,i);
         if(ls!=rs)ans+=abs(ls-rs)-;
     }
     cout<<ans/<<endl;
 }
 int main(){
 //    fre("in.txt","r",stdin);
     freopen("kingdom.in","r",stdin);
     freopen("kingdom.out","w",stdout);
     int t=;
      while(~scanf("%d",&n) &&n)    solve();
     return ;
 }