用C或C++实现给定N个点坐标且N个点依次围成多边形，再给一点（X，Y）判断是否在多边形中

boolean pointInPolygon() {

int i, j=0 ;
boolean oddNODES=FALSE ;

for (i=0; i<polySides; i++) {
j++; if (j==polySides) j=0;
if (polyY[i]<y && polyY[j]>=y
|| polyY[j]<y && polyY[i]>=y) {
if (polyX[i]+(y-polyY[i])/(polyY[j]-polyY[i])*(polyX[j]-polyX[i])<x) {
oddNODES=!oddNODES; }}}

return oddNODES; }

判断点在多边形内一般用扫描线法