深度遍历有向图

问题：用标记来记录是否访问过，这个是个关键点。当然也可以用栈，思想是每访问一个顶点就入栈，接着访问这个顶点的下一个顶点，最后出栈，看出栈的顶点有没有下一个顶点，如果有就继续访问。如此重复，直到栈空。

还有一点就是用到了递归思想。很像二叉树的前序遍历。

代码：

#include <iostream>
#include <cstdlib>
using namespace std;
 
#define MAXV 20
 
typedef struct edgeNode
{
    int data;
    struct edgeNode *next;
}edgeList;
 
typedef struct headNode
{
    char vex;
    edgeList *firstNode;
}headList;
 
typedef struct graph           //定义邻接表结构
{
    headList arr[MAXV];
    int v,e;
}*adjGraph;
 
 
void createAdjGraph(adjGraph &ag)
{
    char c;
    int p,q;
    edgeList *s;
    cout<<"please input the num of v and e:";
    cin>>ag->v>>ag->e;
 
    for(int i=0;i<ag->v;i++)             //初始化头节点
    {
        cout<<"please input vex:";
        cin>>c;
        ag->arr[i].vex=c;
        ag->arr[i].firstNode=NULL;
    }
 
    for(int j=0;j<ag->e;j++)
    {
        cout<<"please input two vexs:";
        cin>>p>>q;
        s=(edgeList *)malloc(sizeof(struct edgeNode));
        s->data=p;
        s->next=ag->arr[q].firstNode;
        ag->arr[q].firstNode=s;
    }
}
 
void showAdjGraph(adjGraph ag)
 {
    for(int i=0;i<ag->v;i++)
    {
        cout<<ag->arr[i].vex<<"  ";
        while(ag->arr[i].firstNode!=NULL)
        {
            cout<<ag->arr[i].firstNode->data<<" ";
            ag->arr[i].firstNode=ag->arr[i].firstNode->next;
        }
        cout<<endl;
    }
}
 
void DFS(adjGraph ag,int v,int *visited)
{
     edgeList *s;
     int w;
     visited[v]=1;
     s=ag->arr[v].firstNode;
     cout<<ag->arr[v].vex<<"->";
     while(s!=NULL)
     {
         w=s->data;
         if(visited[w]==0)
             DFS(ag,w,visited);
         s=s->next;
     }
      
}
void DFSTraversal(adjGraph ag)
{
    int visited[MAXV];
 
    for(int i=0;i<ag->v;i++)
    {
        visited[i]=0;
    }
 
    for(int j=0;j<ag->v;j++)
    {
        if(visited[j]==0)
           DFS(ag,j,visited);
    }
    cout<<endl;
}
int main()
{
    adjGraph ag;
    ag=(adjGraph)malloc(sizeof(struct graph));
    cout<<"创建图:"<<endl;
    createAdjGraph(ag);
    cout<<"输出图"<<endl;
    showAdjGraph(ag);
    cout<<"深度遍历图:"<<endl;
    DFSTraversal(ag);
    return 0;
}