n.跨度；拉线；[数]生成；长成
动词span的现在分词形式.
Study on the Problem of Constrained Minimum Spanning Tree. 约束最小生成树问题研究。
There is a recursive formula for the number of spanning trees in a graph. 对于一个图的生成树的棵数，存在一个递推公式。
