k-d树（k-dimensional树的简称），是一种分割k维数据空间的数据结构。主要应用于多维空间关键数据的搜索（如：范围搜索和最近邻搜索）。用java实现，可直接运行-kd-tree (k-dimensional tree for short), is a partition the data structure of k-dimensional data space. Mainly used in the search of the key data of the multidimensional space (such as: the scope of the search and nearest neighbor search). Java to achieve, can be run directly