The dashed circle shows the current best distance. As the algorithm finds closer points, the circle shrinks, which causes more subtrees to fail the "could contain a closer point?" test and get pruned. The search usually gets cheaper as it progresses.
Kevin Church/ BBC News。同城约会对此有专业解读
。夫子对此有专业解读
Юлия Мискевич (Ночной линейный редактор)
* @return pivot最终位置，这一点在快连下载安装中也有详细论述