hdu 1756 判断点在多边形内 *

模板题

 #include<cstdio>
 #include<iostream>
 #include<algorithm>
 #include<cstring>
 #include<cmath>
 #include<queue>
 #define lson l,mid,rt<<1
 #define rson mid+1,r,rt<<1|1
 #define root 1,n,1
 #define mid ((l+r)>>1)
 #define ll long long
 #define cl(a) memset(a,0,sizeof(a))
 #define ts printf("*****\n");
 using namespace std;
 const int MAXN=+;
 int sum[MAXN<<],lsum[MAXN<<],rsum[MAXN<<];
 int n,m,tt;
 const double eps = 1e-;
 const double PI = acos(-1.0);
 int sgn(double x)
 {
 if(fabs(x) < eps)return ;
 if(x < )return -;
 else return ;
 }
 struct Point
 {
 double x,y;
 Point(){}
 Point(double _x,double _y)
 {
 x = _x;y = _y;
 }
 Point operator -(const Point &b)const
 {
 return Point(x - b.x,y - b.y);
 }
 //叉积
 double operator ^(const Point &b)const
 {
 return x*b.y - y*b.x;
 }
 //点积
 double operator *(const Point &b)const
 {
 return x*b.x + y*b.y;
 }
 //绕原点旋转角度B（弧度值），后x,y的变化
 void transXY(double B)
 {
     double tx = x,ty = y;
     x = tx*cos(B) - ty*sin(B);
     y = tx*sin(B) + ty*cos(B);
 }
 };
 //*判断点在线段上
 struct Line
 {
 Point s,e;
 Line(){}
 Line(Point _s,Point _e)
 {
 s = _s;e = _e;
 }
 //两直线相交求交点
 //第一个值为0表示直线重合，为1表示平行，为0表示相交,为2是相交
 //只有第一个值为2时，交点才有意义
 pair<int,Point> operator &(const Line &b)const
 {
 Point res = s;
 if(sgn((s-e)^(b.s-b.e)) == )
 {
 if(sgn((s-b.e)^(b.s-b.e)) == )
 return make_pair(,res);//重合
 else return make_pair(,res);//平行
 }
 double t = ((s-b.s)^(b.s-b.e))/((s-e)^(b.s-b.e));
 res.x += (e.x-s.x)*t;
 res.y += (e.y-s.y)*t;
 return make_pair(,res);
 }
 };
 bool OnSeg(Point P,Line L)
 {
 return
 sgn((L.s-P)^(L.e-P)) ==  &&
 sgn((P.x - L.s.x) * (P.x - L.e.x)) <=  &&
 sgn((P.y - L.s.y) * (P.y - L.e.y)) <= ;
 }
 bool inter(Line l1,Line l2)
 {
 return
 max(l1.s.x,l1.e.x) >= min(l2.s.x,l2.e.x) &&
 max(l2.s.x,l2.e.x) >= min(l1.s.x,l1.e.x) &&
 max(l1.s.y,l1.e.y) >= min(l2.s.y,l2.e.y) &&
 max(l2.s.y,l2.e.y) >= min(l1.s.y,l1.e.y) &&
 sgn((l2.s-l1.e)^(l1.s-l1.e))*sgn((l2.e-l1.e)^(l1.s-l1.e)) <=  &&
 sgn((l1.s-l2.e)^(l2.s-l2.e))*sgn((l1.e-l2.e)^(l2.s-l2.e)) <= ;
 }
 //*判断点在任意多边形内
 //射线法，poly[]的顶点数要大于等于3,点的编号0~n-1
 //返回值
 //-1:点在凸多边形外
 //0:点在凸多边形边界上
 //1:点在凸多边形内
 int inPoly(Point p,Point poly[],int n)
 {
 int cnt;
 Line ray,side;
 cnt = ;
 ray.s = p;
 ray.e.y = p.y;
 ray.e.x = -100000000000.0;//-INF,注意取值防止越界
 for(int i = ;i < n;i++)
 {
 side.s = poly[i];
 side.e = poly[(i+)%n];
 if(OnSeg(p,side))return ;
 //如果平行轴则不考虑
 if(sgn(side.s.y - side.e.y) == )
 continue;
 if(OnSeg(side.s,ray))
 {
 if(sgn(side.s.y - side.e.y) > )cnt++;
 }
 else if(OnSeg(side.e,ray))
 {
 if(sgn(side.e.y - side.s.y) > )cnt++;
 }
 else if(inter(ray,side))
 cnt++;
 }
 if(cnt %  == )return ;
 else return -;
 }

 Point a[MAXN],b;
 int main()
 {
     int i,j,k;
     #ifndef ONLINE_JUDGE
     freopen("1.in","r",stdin);
     #endif
     while(scanf("%d",&n)!=EOF)
     {
         for(i=;i<n;i++)
         {
             scanf("%lf%lf",&a[i].x,&a[i].y);
         }
         scanf("%d",&m);
         for(i=;i<m;i++)
         {
             scanf("%lf%lf",&b.x,&b.y);
             if(inPoly(b,a,n)!=-)
             {
                 printf("Yes\n");
             }
             else   printf("No\n");
         }
     }
 }