Centroid

代码说明：

  质心定位算法源码，分三种情况考虑，只有锚节点，被定位到的未知节点也作为锚节点，有邻居锚节点的未知节点只利用邻居锚节点进行定位，没有邻居锚节点的未知节点才利用已经定位了的邻居未知节点进行定位。 (Centroid localization algorithm source，Three cases to consider.Only the anchor nodes,unknown nodes to be positioned as anchor nodes,neighbor anchor node of the unknown node using only neighbor anchor node positioning, not unknown neighbor anchor node node neighbor has positioned the unknown node positioning.)