#include
#include
#include?
#define?max（ab）?（（a>b）?a:b）
#define?min（ab）?（（ausing?namespace?std;

const?double?INFINITY?=?1e10;?
const?double?ESP?=?1e-5;?
const?int?MAX_N?=?1000;?
//定義點
?struct?Point?
{?
	double?x?y;?
};?
//定義邊

struct?LineSegment?
{?
	Point?pt1?pt2;?
};?

typedef?vector?Polygon;?
?

//?計算叉乘?|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）?）;?
}?

//?判斷線段是否包含點point?
bool?IsOnline（Point?point?LineSegment?line）?
{?
	return（?（?fabs（Multiply（line.pt1?line.pt2?point））?	（?（?point.x?-?line.pt1.x?）?*?（?point.x?-?line.pt2.x?）?<=?0?）?&&?
	（?（?point.y?-?line.pt1.y?）?*?（?point.y?-?line.pt2.y?）?<=?0?）?）;?
}?

//?判斷線段相交?
bool?Intersect（LineSegment?L1?LineSegment?L2）?
{?
	return（?（max（L1.pt1.x?L1.pt2.x）?>=?min（L2.pt1.x?L2.pt2.x））?&&?
	（max（L2.pt1.x?L2.pt2.x）?>=?min（L1.pt1.x?L1.pt2.x））?&&?
	（max（L1.pt1.y?L1.pt2.y）?>=?min（L2.pt1.y?L2.pt2.y））?&&?
	（max（L2.pt1.y?L2.pt2.y）?>=?min（L1.pt1.y?L1.pt2.y））?&&?
	（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）?
	）;?
}?

//?判斷點在多邊形內(nèi)?
bool?InPolygon（Polygon?&?polygon?Point?point）?
{?
	int?n?=?polygon.size（）;?
	int?count?=?0;?
	LineSegment?line;?
	line.pt1?=?point;?
	line.pt2.x?=?point.x;?
	line.pt2.y?=?-?INFINITY;?
?
	for（?int?i?=?0;?i?	//?得到多邊形的一條邊?
	LineSegment?side;?
	side.pt1?=?polygon[i];?
	side.pt2?=?polygon[（i?+?1）?%?n];?
	?//判斷已知點是否在邊上
	if（?IsOnline（point?side）?）?{?
	return?1?;
	}?
?
	//?如果side平行y軸則不作考慮?
	if（?fabs（side.pt1.x?-?side.pt2.x）?	continue;?
	}?
?
	if（?IsOnline（side.pt1?line）?）?
	{?
	if（?side.pt1.x?>?side.pt2.x?）?count++;?
	}?
	else?if（?IsOnline（side.pt2?line）?）?
	{?
	if（?side.pt2.x>?side.pt1.x?）?count++;?
	}?
	else?if（?Intersect（line?side）?）
	{?
	count++;?
	}?
	}?
?
	?if?（?count?%?2?==?1?）?{return?0;}
	else?{?return?1;}
}



//****************************************************************
void?main（）
{
	int?n;
	double?xy;

	Point?pt1;
	cout<<“請輸入一點：“<	cin>>x>>y;
	pt1.x=x;
	pt1.y=y;
	cout<<“點坐標(biāo)為：（“<
	Polygon?poly;
	cout<<“請輸入多邊形的邊數(shù)：“<	cin>>n;
	for（int?i=0;i	{
		double?mj;
		cout<<“請輸入第“<		cin>>m>>j;
		Point?pt;
		pt.x=m;
		pt.y=j;
		poly.push_back（pt）;
	}
	
	//cout<<“多邊形的邊數(shù)“<	bool?retur;
	retur=InPolygon（poly?pt1）;?
	if（retur==1）
		cout<<“點在多邊形外！“<	else?
		cout<<“點在多邊形內(nèi)！“<
}

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件??????31521??2011-03-24?21:53??點在多邊形內(nèi)Y軸C++\Debug\PInP.obj

?????文件?????241724??2011-03-24?21:53??點在多邊形內(nèi)Y軸C++\Debug\PInPVC.exe

?????文件?????296968??2011-03-24?21:53??點在多邊形內(nèi)Y軸C++\Debug\PInPVC.ilk

?????文件????1281284??2011-03-11?18:52??點在多邊形內(nèi)Y軸C++\Debug\PInPVC.pch

?????文件?????582656??2011-03-24?21:52??點在多邊形內(nèi)Y軸C++\Debug\PInPVC.pdb

?????文件??????74752??2011-03-24?21:57??點在多邊形內(nèi)Y軸C++\Debug\vc60.idb

?????文件??????94208??2011-03-24?21:52??點在多邊形內(nèi)Y軸C++\Debug\vc60.pdb

?????文件???????2820??2011-03-24?21:52??點在多邊形內(nèi)Y軸C++\PInP.cpp

?????文件???????4282??2011-03-11?19:13??點在多邊形內(nèi)Y軸C++\PInPVC.dsp

?????文件????????520??2011-03-11?18:50??點在多邊形內(nèi)Y軸C++\PInPVC.dsw

?????文件??????41984??2011-03-24?21:57??點在多邊形內(nèi)Y軸C++\PInPVC.ncb

?????文件??????53760??2011-03-24?21:57??點在多邊形內(nèi)Y軸C++\PInPVC.opt

?????文件????????246??2011-03-24?21:54??點在多邊形內(nèi)Y軸C++\PInPVC.plg

?????目錄??????????0??2011-03-24?21:52??點在多邊形內(nèi)Y軸C++\Debug

?????目錄??????????0??2011-03-24?21:57??點在多邊形內(nèi)Y軸C++

-----------?---------??----------?-----??----

??????????????2706725????????????????????15