0001 template <typename Tv, typename Te> //深度优先搜索（单个可达分量）
0002 void Graph<Tv, Te>::DFS(Rank v, Rank& clock) { //0 <= v < n
0003    dTime(v) = clock++;  status(v) = DISCOVERED; //发现当前顶点v
0004    for (Rank u = firstNbr(v); -1 != u; u = nextNbr(v, u)) //考查v的每一个邻居u
0005       switch (status(u)) { //并视其状态分别处理
0006          case UNDISCOVERED : //u尚未发现，意味着支撑树可在此拓展
0007             type(v, u) = TREE;  parent(u) = v;  DFS(u, clock);  break;
0008          case DISCOVERED : //u已被发现但尚未访问完毕，应属被后代指向的祖先
0009             type(v, u) = BACK;  break;
0010          default : //VISITED：视承袭关系分为前向边或（有向图才可能有的）跨边
0011             type(v, u) = dTime(v) < dTime(u) ? FORWARD : CROSS;  break;
0012       }
0013    status(v) = VISITED;  fTime(v) = clock++; //至此，当前顶点v方告访问完毕
0014 } //DFS