图的深度优先遍历算法

      图的深度优先遍历类似于树的先根遍历，首先访问顶点v0，再访问v0的邻接点v1，同样递归访问v1的邻接点，若到vi时的所有邻接点均以访问完毕，则退回上一个顶点查看是否有邻接点为被访问，若有临界点w未被访问，则访问递归w，否则继续退回前一个结点。全部结点访问完毕时，算法结束。

      给出邻接表表示的图的递归和非递归算法，下面是图的邻接矩阵和邻接表表示，设置Visited[i]来记录结点i是否被访问。

#include <stdio.h>#include <malloc.h>#define MAXV 50int visited[MAXV];typedef int InfoType;typedef struct {int no;InfoType info;}VertType;typedef struct{int edges[MAXV][MAXV];VertType vexs[MAXV];int n,e;}MGraph;typedef struct ANode{int adjvex;InfoType info;struct ANode *nextarc;}ArcNode;typedef int Vertex;typedef struct{Vertex data;ArcNode *firstarc;}VNode;typedef VNode AdjList[MAXV];typedef struct{AdjList adjlist;int n,e;}ALGraph;

        递归算法如下：

void DFS(ALGraph *G,int v){ArcNode *p;int n=G->n;visited[v] = 1;printf("%3d",v);p = G->adjlist[v].firstarc;while(p){if(visited[p->adjvex] == 0)DFS(G,p->adjvex);p = p->nextarc;}}

        非递归算法如下：

void DFS1(ALGraph *G, int v){ArcNode *p;ArcNode *St[MAXV];int top=-1;int i,w,n=G->n;for(i=0; i<n; i++)visited[i] = 0;visited[v] = 1;printf("%3d",v);top++;St[top] = G->adjlist[v].firstarc;while(top>=0){p = St[top];top--;while(p!=NULL){w = p->adjvex;if(visited[w] == 0){visited[w] = 1;printf("%3d",w);top++;St[top] = G->adjlist[w].firstarc;break;}p = p->nextarc;}}}

void main(){MGraph g;ALGraph *G;int i,j;int A[MAXV][6] = {{0,5,0,7,0,0},{0,0,4,0,0,0},{8,0,0,0,0,9},{0,0,5,0,0,6},{0,0,0,5,0,0},{3,0,0,0,1,0}};g.n = 6;g.e =10;for(i=0; i<g.n; i++)for(j=0; j<g.n; j++)g.edges[i][j] = A[i][j];for(i=0; i<g.n; i++)visited[i] = 0;MatToList(g,G);printf("图G的邻接表:\n");DispList(G);printf("从顶点0开始的DFS(递归算法):\n");DFS(G,0);printf("\n");printf("从顶点0开始的DFS(非递归算法):\n");DFS1(G,0);printf("\n");}

      运行结果：