1.　　用ＤＦＳ判断一个无向图是否是连通图；

2.　　为有向图的边分类，将它们的边分为前向边、后向边和交叉边；

3.　　用ＤＦＳ和点消除求有向图的拓扑排序；

4.　　判断有向图是不是强连通图，若不是，求强连通分量；

5.　　判断有向图是不是半连同图；

6.　　判断有向图是不是单连通图；

7.　　判断无向图是不是双连通图。

通过以上编程对ＤＦＳ的应用，进一步了解ＤＦＳ的算法及它所代表的算法思想。

-1.　　Using DFS to test if a given undirected graph is connected or not.

2.　　Classify the edges of a directed graph into tree edges, back edges, forward edges or cross edges by a depth-first traversal of the graph. If the given graph is undirected, classify the edges into tree edges and back edges. And verify if a directed or undirected graph has a cycle.

3.　　Compute the topological order of a directed graph using both DFS algorithm and source removal algorithm.

4.　　A strongly connected graph is a directed graph with every pair of vertices reachable from each other. A strongly connected component C of a directed graph G is a subset of maximal vertices such that every pair of vertices in the subset are reachable from each other. A strongly connected component graph GSCC of a graph G is a directed graph that each component C of G is considered as a single vertex in GSCC and there is an edge between components C1 and C2 if there exist an edge (u, v) in the graph G with u belongs to C1 and v