Status DFSArticul(MGraph graph, int vex_index, int *count, int articulated[MAXVEX + 1], int visited_sequ[MAXVEX], int vex_can_arrived[MAXVEX]) {
int nextvex;
visited_sequ[vex_index] = *count;
++*count;
vex_can_arrived[vex_index] = visited_sequ[vex_index]; //min(自己的序号，儿子能到达的最早序号，自己的祖先边中祖先的序号)
for (nextvex = FirstAdjVex(graph, vex_index); nextvex != -1; nextvex = NextAdjVex(graph, vex_index, nextvex)) {
if (visited_sequ[nextvex] == -1) {
DFSArticul(graph, nextvex, count, articulated, visited_sequ, vex_can_arrived);
if (vex_can_arrived[nextvex] < vex_can_arrived[vex_index]) {
vex_can_arrived[vex_index] = vex_can_arrived[nextvex];
}
if (vex_can_arrived[nextvex] >= visited_sequ[vex_index]) {
int i;
for (i = 1; i <= articulated[0]; ++i) //如果该点已经添加过了，则不必再添加
if (articulated[i] == graph.vexs[vex_index])
break;
if (i == articulated[0] + 1) {
++articulated[0];
articulated[articulated[0]] = graph.vexs[vex_index];
}
}
}
else if (visited_sequ[nextvex] < vex_can_arrived[vex_index]) {
vex_can_arrived[vex_index] = visited_sequ[nextvex];
}
}
return OK;
}
void FindArticul(ALGraph G)
{ /* 连通图G以邻接表作存储结构，查找并输出G上全部关节点。算法7.10 */
/* 全局量count对访问计数。 */
int i,v;
ArcNode *p;
count=1;
low[0]=visited[0]=1; /* 设定邻接表上0号顶点为生成树的根 */
for(i=1;i<G.vexnum;++i)
visited[i]=0; /* 其余顶点尚未访问 */
p=G.vertices[0].firstarc;
v=p->adjvex;
DFSArticul(G,v); /* 从第v顶点出发深度优先查找关节点 */
if(count<G.vexnum) /* 生成树的根有至少两棵子树 */
{
printf("%d %s\n",0,G.vertices[0].data); /* 根是关节点，输出 */
while(p->nextarc)
{
p=p->nextarc;
v=p->adjvex;
if(visited[v]==0)
DFSArticul(G,v);
}
}
}
void DFSArticul(ALGraph G, int v0 ) { // 算法7.11
// 从第v0个顶点出发深度优先遍历图G，查找并输出关节点
int min,w;
struct ArcNode *p;
visited[v0] = min = ++count; // v0是第count个访问的顶点
for (p=G.vertices[v0].firstarc; p!=NULL; p=p->nextarc) {
// 检查v0的每个邻接顶点
w = p->adjvex; // w为v0的邻接顶点
if (visited[w] == 0) { // w未曾被访问，是v0的孩子
DFSArticul(G, w); // 返回前求得low[w]
if (low[w] < min) min = low[w];
if (low[w] >= visited[v0])
printf(v0, G.vertices[v0].data); // 输出关节点
}
else if (visited[w] < min) min = visited[w];
// w已被访问，w是v0在生成树上的祖先
}//for
low[v0] = min;
} // DFSArticul
void DFSArticul(ALGraph G,int v0)
{ /* 从第v0个顶点出发深度优先遍历图G，查找并输出关节点。算法7.11 */
int min,w;
ArcNode *p;
visited[v0]=min=++count; /* v0是第count个访问的顶点 */
for(p=G.vertices[v0].firstarc;p;p=p->nextarc) /* 对v0的每个邻接顶点检查 */
{
w=p->adjvex; /* w为v0的邻接顶点 */
if(visited[w]==0) /* w未曾访问，是v0的孩子 */
{
DFSArticul(G,w); /* 返回前求得low[w] */
if(low[w]<min)
min=low[w];
if(low[w]>=visited[v0])
printf("%d %s\n",v0,G.vertices[v0].data); /* 关节点 */
}
else if(visited[w]<min)
min=visited[w]; /* w已访问，w是v0在生成树上的祖先 */
}
low[v0]=min;
}
Status FindArticul(MGraph graph, int articulated[MAXVEX + 1]) {
int visited_sequ[MAXVEX]; //被访问的序列号
int vex_can_arrived[MAXVEX]; //能到达的最早被访问的序列号
int index, i;
int count;
if (graph.vexnum < 2)
return ERROR;
if (!articulated)
return ERROR;
articulated[0] = 0;
count = 0;
for (i = 0; i < graph.vexnum; ++i) //访问序列初始化
visited_sequ[i] = -1;
for (i = 0; i < graph.vexnum; ++i) {
if (visited_sequ[i] == -1) {
visited_sequ[i] = count;
++count;
if ((index = FirstAdjVex(graph, i)) == -1) //不能存在度为0的点(独立构成一个连通分量)
return ERROR;
// 对根的一棵子树进行遍历，找出关节点
DFSArticul(graph, index, &count, articulated, visited_sequ, vex_can_arrived);
// 判断根是否是关节点
for (index = FirstAdjVex(graph, i); index != -1; index = NextAdjVex(graph, i, index)) {
if (visited_sequ[index] == -1) {
++articulated[0];
articulated[articulated[0]] = graph.vexs[i];
break;
}
}
}
}
return OK;
}
