这是数据结构中图的广度优先算法的实现。广度优先算法是按照每个节点的拥有的孩子数目来进行遍历的。而不像图的深度优先算法是按照深层次，然后如果不能继续进入更深一层，就往回遍历。-BFS program of tree have a large of difference of the DFS program of trees.The produre of it is with the method of the children of a point ,rather than the depth o