[本文是自己学习所做笔记，欢迎转载，但请注明出处：http://blog.csdn.net/jesson20121020]
算法描述：
假设给定图G的初始状态是所有顶点均未曾访问过，在G中任选一顶点vi为初始的出发点，则深度优先遍历可定义如下： 首先访问出发点vi，并将其标记为已被访问过；然后，依次从vi出发遍历vi的每一个邻接点vj，若vj未曾访问过，则以vj为新的出发点继续进行深度优先遍历，直至图中所有和vi有路径相通的顶点都被访问到为止。因此，若G是连通图，则从初始出发点开始的遍历过程结束也就意味着完成了对图G的遍历。
算法实现：
分别以邻接矩阵和邻接表作为图的存储结构，给出连通图的深度优先搜索遍历的递归算法。算法描述如下：
(1) 访问出发点vi，并将其标记为已被访问已访问过。
(2) 遍历vi的每一个邻接点vj，若vj未曾访问过，则以vj为新的出发点继续进行深度优先遍历。
完整代码：
用邻接矩阵实现深度优先搜索算法源代码如下：
/**
* 深度遍历图
**/
void DFS_MG(MGraph MG,int i){
visit[i] = 1;
printf("%c\t",MG.vexs[i]);
int j;
for (j = 1; j <= MG.vexnum;j++){
if(visit[j] == 0 && MG.arcs[i][j] == 1)
DFS_MG(MG,j);
}
}
用邻接表实现深度优先搜索算法源代码如下：
/**
* 深度遍历图
**/
void DFS_AG(ALGraph AG,int i){
ArcPtr p;
printf("%c\t",AG.vertices[i].vexdata);
visit[i] = 1;
p = AG.vertices[i].firstarc;
while( p!= NULL ){
if(visit[p->adjvex] == 0)
DFS_AG(AG,p->adjvex);
p = p->nextarc;
}
}算法说明：
对于具有n个顶点，e条边的连通图，算法DFS_MG,DFS_AG 均调用n次。除了初始调用是来自外部，基于n-1次调用均是来自DFS_MG和DFS_AG内部的递归调用，用邻接矩阵实现时，遍历一个顶点的所有邻接点需要O(n)时间，则遍历整个图需要O(n^2),即DFS_MG的时间复杂度为O(n^2)。
用邻接表实现时，遍历n个顶点的所有邻接点是对边表节点的扫描一遍，故算法DFS_AG时间复杂度为O(n+e)。
采用深度优先遍历算法时，都要用到访问标志，所以该算法的空间复杂度为O(n).
邻接矩阵实现深度优先搜索算法完整代码如下：
/*
============================================================================
Name : Graph.c
Author : jesson20121020
Version : 1.0
Description : create Graph using Adjacency Matrix, Ansi-style
============================================================================
*/
#include <stdio.h>
#include <stdlib.h>
#define MAX_VEX_NUM 50
typedef char VertexType;
typedef enum {
DG, UDG
} GraphType;
typedef struct {
VertexType vexs[MAX_VEX_NUM];
int arcs[MAX_VEX_NUM][MAX_VEX_NUM];
int vexnum, arcnum;
GraphType type;
} MGraph;
//设置图中顶点访问标志
int visit[MAX_VEX_NUM];
/**
* 根据名称得到指定顶点在顶点集合中的下标
* vex 顶点
* return 如果找到，则返回下标，否则，返回０
*/
int getIndexOfVexs(char vex, MGraph *MG) {
int i;
for (i = 1; i <= MG->vexnum; i++) {
if (MG->vexs[i] == vex) {
return i;
}
}
return 0;
}
/**
* 创建邻接矩阵
*/
void create_MG(MGraph *MG) {
int i, j, k;
int v1, v2, type;
char c1, c2;
printf("Please input graph type DG(0) or UDG(1) :");
scanf("%d", &type);
if (type == 0)
MG->type = DG;
else if (type == 1)
MG->type = UDG;
else {
printf("Please input correct graph type DG(0) or UDG(1)!");
return;
}
printf("Please input vexmun : ");
scanf("%d", &MG->vexnum);
printf("Please input arcnum : ");
scanf("%d", &MG->arcnum);
getchar();
for (i = 1; i <= MG->vexnum; i++) {
printf("Please input %dth vex(char):", i);
scanf("%c", &MG->vexs[i]);
getchar();
}
//初始化邻接矩阵
for (i = 1; i <= MG->vexnum; i++) {
for (j = 1; j <= MG->vexnum; j++) {
MG->arcs[i][j] = 0;
}
}
//输入边的信息，建立邻接矩阵
for (k = 1; k <= MG->arcnum; k++) {
printf("Please input %dth arc v1(char) v2(char) : ", k);
scanf("%c %c", &c1, &c2);
v1 = getIndexOfVexs(c1, MG);
v2 = getIndexOfVexs(c2, MG);
if (MG->type == 1)
MG->arcs[v1][v2] = MG->arcs[v2][v1] = 1;
else
MG->arcs[v1][v2] = 1;
getchar();
}
}
/**
* 打印邻接矩阵和顶点信息
*/
void print_MG(MGraph MG) {
int i, j;
if(MG.type == DG){
printf("Graph type: Direct graph\n");
}
else{
printf("Graph type: Undirect graph\n");
}
printf("Graph vertex number: %d\n",MG.vexnum);
printf("Graph arc number: %d\n",MG.arcnum);
printf("Vertex set:\n ");
for (i = 1; i <= MG.vexnum; i++)
printf("%c\t", MG.vexs[i]);
printf("\nAdjacency Matrix:\n");
for (i = 1; i <= MG.vexnum; i++) {
j = 1;
for (; j < MG.vexnum; j++) {
printf("%d\t", MG.arcs[i][j]);
}
printf("%d\n", MG.arcs[i][j]);
}
}
/**
* 初始化顶点访问标志
**/
void init_Visit(){
int i;
for(i = 0;i < MAX_VEX_NUM;i++)
visit[i] = 0;
}
/**
* 深度遍历图
**/
void DFS_MG(MGraph MG,int i){
visit[i] = 1;
printf("%c\t",MG.vexs[i]);
int j;
for (j = 1; j <= MG.vexnum;j++){
if(visit[j] == 0 && MG.arcs[i][j] == 1)
DFS_MG(MG,j);
}
}
/**
* 主函数
*/
int main(void) {
MGraph MG;
create_MG(&MG);
print_MG(MG);
printf("The result of DFS:\n");
DFS_MG(MG,1);
return EXIT_SUCCESS;
}邻接表实现深度优先搜索算法的完整代码如下：
/*
============================================================================
Name : ALGraph.c
Author : jesson20121020
Version : 1.0
Copyright : Your copyright notice
Description : Graph using linkList, Ansi-style
============================================================================
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdio.h>
#define MAX_VERTEX_NUM 50
typedef enum {
DG, UDG
} GraphType;
typedef char VertexType;
//表节点
typedef struct ArcNode {
int adjvex; //邻接节点
int weight; //边权重
struct ArcNode *nextarc; //下一个节点指针
} ArcNode, *ArcPtr;
//头节点
typedef struct {
VertexType vexdata;
int id;
ArcPtr firstarc;
} VNode;
//头节点数组
typedef struct {
VNode vertices[MAX_VERTEX_NUM];
int vexnum, arcnum;
GraphType type;
} ALGraph;
int visit[MAX_VERTEX_NUM];
/**
* 根据顶点字符得到在顶点数组中的下标
*/
int getIndexOfVexs(char vex, ALGraph *AG) {
int i;
for (i = 1; i <= AG->vexnum; i++) {
if (AG->vertices[i].vexdata == vex) {
return i;
}
}
return 0;
}
/**
* 创建邻接表
*/
void create_AG(ALGraph *AG) {
ArcPtr p,q;
int i, j, k, type;
VertexType v1, v2;
printf("Please input graph type UG(0) or UDG(1) :");
scanf("%d", &type);
if (type == 0)
AG->type = DG;
else if (type == 1)
AG->type = UDG;
else {
printf("Please input correct graph type UG(0) or UDG(1)!");
return;
}
printf("please input vexnum:");
scanf("%d", &AG->vexnum);
printf("please input arcnum:");
scanf("%d", &AG->arcnum);
getchar();
for (i = 1; i <= AG->vexnum; i++) {
printf("please input the %dth vex(char) : ", i);
scanf("%c", &AG->vertices[i].vexdata);
getchar();
AG->vertices[i].firstarc = NULL;
}
for (k = 1; k <= AG->arcnum; k++) {
printf("please input the %dth arc v1(char) v2(char) :", k);
scanf("%c %c", &v1, &v2);
i = getIndexOfVexs(v1, AG);
j = getIndexOfVexs(v2, AG);
//根据图的类型创建邻接表
//方法1，插入到链表头
/*
if (AG->type == DG) { //有向图
p = (ArcPtr) malloc(sizeof(ArcNode));
p->adjvex = j;
p->nextarc = AG->vertices[i].firstarc;
AG->vertices[i].firstarc = p;
} else { //无向图
p = (ArcPtr) malloc(sizeof(ArcNode));
p->adjvex = j;
p->nextarc = AG->vertices[i].firstarc;
AG->vertices[i].firstarc = p;
p = (ArcPtr) malloc(sizeof(ArcNode));
p->adjvex = i;
p->nextarc = AG->vertices[j].firstarc;
AG->vertices[j].firstarc = p;
}
*/
//方法2，插入到链表尾
if (AG->type == DG) { //有向图
p = (ArcPtr) malloc(sizeof(ArcNode));
p->adjvex = j;
//表为空
if(AG->vertices[i].firstarc == NULL){
AG->vertices[i].firstarc = p;
}
else{
//找最后一个表节点
q = AG->vertices[i].firstarc;
while(q->nextarc != NULL){
q = q->nextarc;
}
q->nextarc = p;
}
p->nextarc = NULL;
} else { //无向图
p = (ArcPtr) malloc(sizeof(ArcNode));
p->adjvex = j;
//表为空
if(AG->vertices[i].firstarc == NULL){
AG->vertices[i].firstarc = p;
}
else{
//找最后一个表节点
q = AG->vertices[i].firstarc;
while(q->nextarc != NULL){
q = q->nextarc;
}
q->nextarc = p;
}
p->nextarc = NULL;
p = (ArcPtr) malloc(sizeof(ArcNode));
p->adjvex = i;
//表为空
if(AG->vertices[j].firstarc == NULL){
AG->vertices[j].firstarc = p;
}
else{
//找最后一个表节点
q = AG->vertices[j].firstarc;
while(q->nextarc != NULL){
q = q->nextarc;
}
q->nextarc = p;
}
p->nextarc = NULL;
}
getchar();
}
}
/**
* 输出图的相关信息
*/
void print_AG(ALGraph AG) {
ArcPtr p;
int i;
if (AG.type == DG) {
printf("Graph type: Direct graph\n");
} else {
printf("Graph type: Undirect graph\n");
}
printf("Graph vertex number: %d\n", AG.vexnum);
printf("Graph arc number: %d\n", AG.arcnum);
printf("Vertex set :\n");
for (i = 1; i <= AG.vexnum; i++)
printf("%c\t", AG.vertices[i].vexdata);
printf("\nAdjacency List:\n");
for (i = 1; i <= AG.vexnum; i++) {
printf("%d", i);
p = AG.vertices[i].firstarc;
while (p != NULL) {
printf("-->%d", p->adjvex);
p = p->nextarc;
}
printf("\n");
}
}
/**
* 初始化顶点访问标志
**/
void init_Visit(){
int i;
for(i = 0;i < MAX_VERTEX_NUM;i++)
visit[i] = 0;
}
/**
* 深度遍历图
**/
void DFS_AG(ALGraph AG,int i){
ArcPtr p;
printf("%c\t",AG.vertices[i].vexdata);
visit[i] = 1;
p = AG.vertices[i].firstarc;
while( p!= NULL ){
if(visit[p->adjvex] == 0)
DFS_AG(AG,p->adjvex);
p = p->nextarc;
}
}
int main(void) {
ALGraph AG;
create_AG(&AG);
print_AG(AG);
printf("The result of DFS:\n");
DFS_AG(AG,1);
return EXIT_SUCCESS;
}