c – 在qsort之后标识项目/类指针

我正在深入研究c的三角测量库,它在运行它的三角测量方法之前对一组结构指针进行排序.我试图在我的应用程序中跟踪一个特定的结构指针(XYZ),它根据鼠标位置进行更新.问题是,无论何时应用qsort方法,该指针都会改变.如何识别或跟踪此结构XYZ指针？

这是结构&分类…

struct XYZ{
  double x,y,z;
};

int XYZCompare(const void *v1,const void *v2){
  XYZ *p1,*p2;

  p1 = (XYZ*)v1;
  p2 = (XYZ*)v2;
  if(p1->x < p2->x)
    return(-1);
  else if(p1->x > p2->x)
         return(1);
       else
         return(0);
}

用于鼠标指针引用的XYZ结构数组(此处为2个用于测试)…

XYZ *allPointers = new XYZ[100];
allPointers[0].x = 100;
allPointers[0].y = 200;
allPointers[0].z = 0;
allPointers[1].x = 50;
allPointers[1].y = 80;
allPointers[1].z = 0;
XYZ *mousePointer = &allPointers[0];

排序和更新鼠标方法.

mousePointer->x = mouseX;
mousePointer->y = mouseY;

// If I don't qsort here the reference is fine,but I need to.
qsort(allPointers,2,sizeof(XYZ),XYZCompare); 
// triangulate,etc