import java.util.ArrayList;
import java.util.List;
/**
*
*
* 2012-5-25下午4:37:31
*/
public class SystemTaskJob {
double INFINITY = 1e10;
double ESP = 1e-5;
int MAX_N = 1000;
List<Point> Polygon;
// 计算叉乘 |P0P1| × |P0P2|
double Multiply(Point p1, Point p2, Point p0){
return ( (p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y) );
}
// 判断线段是否包含点point
private boolean IsOnline(Point point, LineSegment line)
{
return( ( Math.abs(Multiply(line.pt1毛泽东七律长征, line.pt2, point)) < ESP ) &&
( ( point.x - line.pt1.x ) * ( point.x - line.pt2.x ) <= 0 ) &&
( ( point.y - line.pt1.y ) * ( point.y - line.pt2.y ) <= 0 ) );
}
// 判断线段相交
成熟的网名男网名 private boolean看酿酒 Interct(LineSegment L1, LineSegment L2)
{
return( (Math.女包十大品牌max(L1.pt1.x, L1.pt2.x) >= Math.min(L2.pt1.x, L2.pt2.x)) &&
(Math.max(L2.pt1.x, L2.pt2.x) >= Math.min(L1.pt1.x, L1.pt2.x)) &&
(Math.max(L1.pt1.我爱你英文怎么说y, L1.pt2.y) >= Math.min(L2.pt1.y, L2.pt2.y)) &&
(Math.max(L2.pt1.y, L2.pt2.y) >= Math.min(L1.pt1.y, L1.pt2.y空间之随遇而安)) &&
(Multiply(L2.pt1, L1.pt2, L1.pt1) * Multiply(L1.pt2, L2.pt2, L1.pt1) >= 0) &&
(Multiply(L1.pt1, L2.pt2, L2.pt1) * Multiply(L2.pt2, L1.pt2, L2.pt1) >= 0)
);
}
/* 射线法判断点q与多边形polygon的位置关系，要求polygon为简单多边形，顶点逆时针排列
如果点在多边形内： 返回0
如果点在多边形边上： 返回1
如果点在多边形外： 返回2
*/
public int InPolygon(List<Point> polygon, Point point)
{
int n = polygon.size();
int count = 0;
LineSegment line = new LineSegment();
line.pt1 = point;
line.pt2.y = point.y;
line.pt2.x = - INFINITY;
for( int i = 0; i < n; i++ ) {
// 得到多边形的一条边
LineSegment side = new LineSegment();
side.pt1 = (i);
side.pt2 = ((i + 1) % n);
if( IsOnline(point, side) ) {
return 1 ;
}
// 如果side平行x轴则不作考虑
if( Math.abs(side.pt1.y - side.pt2.y) < ESP ) {
continue;
}
if( IsOnline(side.黄豆怎么炒pt1, line) ) {
if( side.pt1.y > side.pt2.y ) count++;
} el if( IsOnline(side.pt2岸的成语, line) ) {
if( side.pt2.y > side.pt1.y ) count++;
} el if( Interct(line, side) ) {
count++;
}
}
if ( count % 2 == 1 )
{
return 0;
}
el
{
return 2;
}
}
public static void main(String[] args)
{
SystemTaskJob systemTaskJob = new SystemTaskJob();
List<Point> polygon = new ArrayList<Point>();
Point point1 = new Point(4,9);
Point point2 = new Point(7,10);
Point point3 = new Point(8,2);
Point point4 = new Point(6,8);
Point point5 = new Point(6,9);
Point checkpoint = new Point(7,11);
polygon.add(point1);
polygon.add(point2);
polygon.add(point3);
polygon.add(point4);
polygon.add(point5);
int m = systemTaskJob.InPolygon(polygon, checkpoint);
System.out.println("========="+m);
}
}
class Point
{
public double x;
public double y;
public Point()
{}
public Point(double x,double y)
{
this.x=x;
this.y=y;
}
}
class LineSegment
{
public Point pt1;
public Point pt2;
public LineSegment()
{
this.pt1 = new Point();
this.pt2 = new Point();
}
}
