#include <stdio.h>
#include <stdlib.h>
#define MAX_VERTEX_NUM 20
#define MAX 20
int visited[MAX];
typedef struct ArcNode{
    int adjvex;
    struct ArcNode *next;
}ArcNode;
typedef struct VNode{
int data;
ArcNode * firstarc;
}VNode,AdjList[MAX_VERTEX_NUM];
typedef struct{
    AdjList vertices;
    int vexnum ,arcnum;
}ALGraph;
void Init_ALGraph(ALGraph *a)
{
    int V1,V2,S;
    ArcNode *p;
    int m,i,j;
    printf("请分别输入图的顶点数和边数:\n");
    scanf("%d",&i);
    scanf("%d",&j);
    a->vexnum=i;
    a->arcnum=j;
    printf("请输入各节点数据\n");
    for(i=0;i<a->vexnum;i++)
    { 
        scanf("%d",&(a->vertices[i].data));
        (a->vertices[i]).firstarc=NULL;
    }


    for(S=1;S<=a->arcnum;S++)
    {    printf("请输一条边的两个顶点的数据:\n");
        scanf("%d",&V1);
        scanf("%d",&V2);
        for(i=0;V1!=a->vertices[i].data;i++);
            for(j=0;V2!=a->vertices[j].data;j++);
                p=(ArcNode *)malloc(sizeof(ArcNode));
                p->adjvex=j;
                p->next=a->vertices[i].firstarc;
                a->vertices[i].firstarc=p;
                p=(ArcNode *)malloc(sizeof(ArcNode));
                p->adjvex=i;
                p->next=a->vertices[j].firstarc;
                a->vertices[j].firstarc=p;
       
    }
}

    void DFS(ALGraph a,int v)
    {
        ArcNode *L;
        visited[v]=1;
        printf("深度优先遍历次序为:%d\t",a.vertices[v].data);
        for(L=a.vertices[v].firstarc;L!=NULL;L=L->next)
        {
            DFS(a,L->adjvex);
        }
    }
    void DFSTraverse(ALGraph a)
    {
        int v,m;
        for(v=0;v<a.vexnum;++v)
            visited[v]=0;
        printf("请输入最先遍历的节点数据:\n");
        scanf("%d",&v);
        for(m=0;a.vertices[m].data!=v;m++);
            for(v=m;v<a.vexnum;v++)
                if(!visited[v])
                    DFS(a,v);
                for(v=0;v<m;v++)
                    if(!visited[v])
                        DFS(a,v);
    }
    int main()
    {
        ALGraph a;
        printf("邻接表存储图的结构\n");
        Init_ALGraph(&a);
        printf("深度优先遍历图显示如下:\n");
        DFSTraverse(a);
        return 0;
    }

            

用VC断点调试下

typedef struct VNode{
 int data;
 ArcNode * firstarc;
 }VNode,AdjList[MAX_VERTEX_NUM];
 typedef struct{
     AdjList vertices;      // 这句有没有问题？？     
     int vexnum ,arcnum;
 }ALGraph;