使用鄰接矩陣+棧的形式實現深度優先搜尋，棧中儲存訪問過的節點，後進先出的結構可以讓他回退搜尋未訪問過的節點。

//DFS，使用 鄰接矩陣+棧 實現
#include <iostream>
#include <stack>

using namespace std;

#define MAX_VERTS 20

class Vertex
{
public:
	Vertex(char lab)
	{
		Label = lab;
		wasVisited = false;
	}
public:
	bool wasVisited;
	char Label;
};

class Graph
{
public:
	Graph();
	~Graph();
	void addVertex(char lab);
	void addEdge(int start, int end);
	void printMatrix();
	void showVertex(int v);
	void DFS();
private:
	Vertex* vertexList[MAX_VERTS];
	int nVerts;
	int adjMat[MAX_VERTS][MAX_VERTS];

	int getAdjUnvisitedVertex(int v);
};

Graph::Graph()
{
	nVerts = 0;
	for (int i = 0; i < MAX_VERTS; i++)
	{
		for (int j = 0; j < MAX_VERTS; j++)
		{
			adjMat[i][j] = 0;
		}
	}
}

Graph::~Graph()
{
	//delete[] vertexList;
}
//新增頂點
void Graph::addVertex(char lab)
{
	vertexList[nVerts++] = new Vertex(lab);
}
//新增邊
void Graph::addEdge(int start, int end)
{
	adjMat[start][end] = 1;
	adjMat[end][start] = 1;
}

void Graph::printMatrix()
{
	for (int i = 0; i < nVerts; i++)
	{
		for (int j = 0; j < nVerts; j++)
		{
			cout << adjMat[i][j] << " ";
		}
		cout << endl;
	}
}
//顯示頂點標籤
void Graph::showVertex(int v)
{
	cout << vertexList[v]->Label << " ";
}

//獲得未訪問過的下一個頂點
int Graph::getAdjUnvisitedVertex(int v)
{
	for (int j = 0; j < nVerts; j++)
	{
		//鄰接的並且沒被訪問過
		if ((adjMat[v][j] == 1) && (vertexList[j]->wasVisited == false))
			return j;
	}

	return -1;
}
//深度優先搜尋
void Graph::DFS()
{
	stack<int> gStack;
	vertexList[0]->wasVisited = true;
	showVertex(0);
	//要把訪問過的頂點壓入棧中
	gStack.push(0);
	int v;
	while (gStack.size() > 0)
	{
		//訪問當前頂點的下一個
		v = getAdjUnvisitedVertex(gStack.top());
		//如果沒找到就利用棧向回找
		if (v == -1)
			gStack.pop();
		else
		{
			vertexList[v]->wasVisited = true;
			showVertex(v);
			gStack.push(v);
		}
	}
	cout << endl;
	//為了下一次搜尋再把wasVisited變成false
	for (int j = 0; j < nVerts; j++)
		vertexList[j]->wasVisited = false;
}

int main()
{
	Graph g;
	g.addVertex('A');
	g.addVertex('B');
	g.addVertex('C');
	g.addEdge(0, 1);
	g.addEdge(0, 2);
	
	g.printMatrix();

	g.DFS();

	system("pause");
	return 0;
}