ZOJ 1081 Points Within

# include <stdio.h>
  typedef struct point
  {
      int x,y;
  }Point;
  Point v[105];
  int main()
  {
      int i,n,m,cur,nex,ans,f,t=1;
      Point p;
      while(scanf("%d",&n),n)
      {
          scanf("%d",&m);
          for(i=1;i<=n;i++)
            scanf("%d%d",&v[i].x,&v[i].y);
          if(t!=1)
            putchar('\n');
          printf("Problem %d:\n",t++);
          while(m--)
          {
              scanf("%d%d",&p.x,&p.y);
              for(i=1;i<=n;i++)
                v[i].x-=p.x,v[i].y-=p.y;
              nex=v[1].x>=0?(v[1].y>=0?1:4):(v[1].y>=0?2:3);
              for(i=1,ans=0;i<=n;i++)
              {
                  f=v[i].x*v[i%n+1].y-v[i%n+1].x*v[i].y;
                  if((!v[i].x&&!v[i].y)||(!f&&v[i].x*v[i%n+1].x<=0&&v[i].y*v[i%n+1].y<=0))
                    break;
                  cur=nex;
                  nex=v[i%n+1].x>=0?(v[i%n+1].y>=0?1:4):(v[i%n+1].y>=0?2:3);
                  if(cur%4+1==nex)
                    ans+=1;
                  else if(cur%4+2==nex||cur%4-2==nex)
                    ans+=(f>0?2:-2);
                  else if(nex%4+1==cur)
                    ans-=1;
              }
              if(i<=n||ans)
                printf("Within\n");
              else
                printf("Outside\n");
              for(i=1;i<=n;i++)
                v[i].x+=p.x,v[i].y+=p.y;
          }
      }
      return 0;
  }