graph_dfs

package edu.xidian.graph;

class MyStack {
	private final int SIZE = 20;
	private int[] st;
	private int top;

	public MyStack() {
		st = new int[SIZE];
		top = -1;
	}

	public void push(int j) {
		st[++top] = j;
	}

	public int pop() {
		return st[top--];
	}

	public int peek() {
		return st[top];
	}

	public boolean isEmpty() {
		return (top == -1);
	}
}

class Vertex {
	public char label;
	public boolean wasVisited;

	public Vertex(char lab) {
		label = lab;
		wasVisited = false;
	}
}

public class Graph {
	private final int MAX_VERTS = 20;
	private Vertex vertexList[];
	private int adjMat[][];
	private int nVerts;
	private MyStack theStack;

	public Graph() {
		vertexList = new Vertex[MAX_VERTS];
		adjMat = new int[MAX_VERTS][MAX_VERTS];
		nVerts = 0;
		theStack = new MyStack();
	}

	public void addVertex(char label) {
		vertexList[nVerts++] = new Vertex(label);
	}

	public void addEdge(int start, int end) {
		adjMat[start][end] = 1;
		adjMat[end][start] = 1;
	}

	public void displayVertex(int v) {
		System.out.print(vertexList[v].label);
	}

	public void dfs() {
		vertexList[0].wasVisited = true;
		displayVertex(0); 
		theStack.push(0);
		while (!theStack.isEmpty()) {
			int v = getAdjUnvisitedVertex(theStack.peek());
			if (v == -1) {
				theStack.pop();
			} else {
				vertexList[v].wasVisited = true; 
				displayVertex(v); 
				theStack.push(v);
			}
		}
		for (int j = 0; j < nVerts; j++) {
			vertexList[j].wasVisited = false;
		}
	}

	public int getAdjUnvisitedVertex(int v) {
		for (int j = 0; j < nVerts; j++) {
			if (adjMat[v][j] == 1 && vertexList[j].wasVisited == false) {
				return j;
			}
		}
		return -1;
	}

	public static void main(String[] args) {
		Graph theGraph = new Graph();
		theGraph.addVertex('A'); // 0 (start for dfs)
		theGraph.addVertex('B'); // 1
		theGraph.addVertex('C'); // 2
		theGraph.addVertex('D'); // 3
		theGraph.addVertex('E'); // 4

		theGraph.addEdge(0, 1); // AB
		theGraph.addEdge(1, 2); // BC
		theGraph.addEdge(0, 3); // AD
		theGraph.addEdge(3, 4); // DE

		System.out.print("Visits: ");
		theGraph.dfs();
		System.out.println();
	}
}