图的深度优先搜索(DFS),广度优先搜索(BFS)与最小生成树(MST)

DFS

package org.exam.ch13.dfs;

/**
* Created by xin on 15.10.18.
*/
class StackX {
private final int SIZE = 20;
private int[] st;
private int top;
public StackX() {
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 label) {
this.label = label;
}
}
class Graph{
private final int MAX_VERTS=20;
private Vertex[] vertexList;
private int[][] adjMat;
private int nVerts;//默认值为0
private StackX stackX;
public Graph(){
vertexList=new Vertex[MAX_VERTS];//里面元素为空
adjMat=new int[MAX_VERTS][MAX_VERTS];//元素默认值都为0
stackX=new StackX();
}
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 index){
System.out.print(vertexList[index].label);
}
public int getAdjUnvisitedVertex(int v){
for (int i = 0; i < nVerts; i++) {
if (adjMat[v][i]==1&&vertexList[i].wasVisited==false){
return i;
}
}
return -1;
}
public void dfs(){
vertexList[0].wasVisited=true;
displayVertex(0);
stackX.push(0);
while (!stackX.isEmpty()){
int curVertex=stackX.peek();
int v=getAdjUnvisitedVertex(curVertex);
if (v==-1){
stackX.pop();
}else{
vertexList[v].wasVisited=true;
displayVertex(v);
stackX.push(v);
}
}
for (int i = 0; i < nVerts; i++) {
vertexList[i].wasVisited=false;
}
}
}
public class App {
public static void main(String[] args) {
Graph graph = new Graph();
graph.addVertex('A');
graph.addVertex('B');
graph.addVertex('C');
graph.addVertex('D');
graph.addVertex('E');

graph.addEdge(0,1);
graph.addEdge(1,2);
graph.addEdge(0,3);
graph.addEdge(3,4);
System.out.println("Visits:");
graph.dfs();
System.out.println();
}
}

BFS

package org.exam.ch13.bfs;

/**
* Created by xin on 15.10.20.
*/
class Queue {
private final int SIZE = 20;
private int[] queArray;
private int front;
private int rear;
public Queue() {
queArray = new int[SIZE];
front = 0;
rear = -1;
}
public void insert(int j) {
if (rear == SIZE - 1)
rear = -1;
queArray[++rear] = j;
}
public int remove() {
int temp = queArray[front++];
if (front == SIZE)
front = 0;
return temp;
}
public boolean isEmpty() {
return (rear + 1 == front || (front + SIZE - 1 == rear));
}
}
class Vertex {
public char label;        // label (e.g. 'A')
public boolean wasVisited;

public Vertex(char lab) {
label = lab;
wasVisited = false;
}
}
class Graph{
private final int MAX_VERTS=20;
private Vertex[] vertexList;
private int[][] adjMat;
private int nVerts;//默认值为0
private Queue queue;
public Graph(){
vertexList=new Vertex[MAX_VERTS];//里面元素为空
adjMat=new int[MAX_VERTS][MAX_VERTS];//元素默认值都为0
queue=new Queue();
}
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 index){
System.out.print(vertexList[index].label);
}
public int getAdjUnvisitedVertex(int v){
for (int i = 0; i < nVerts; i++) {
if (adjMat[v][i]==1&&vertexList[i].wasVisited==false){
return i;
}
}
return -1;
}
public void bfs(){
vertexList[0].wasVisited=true;
displayVertex(0);
queue.insert(0);
int v2;

while (!queue.isEmpty()) {     // until queue empty,
int v1 = queue.remove();   // remove vertex at head
// until it has no unvisited neighbors
while ((v2 = getAdjUnvisitedVertex(v1)) != -1) {                                  // get one,
vertexList[v2].wasVisited = true;  // mark it
displayVertex(v2);                 // display it
queue.insert(v2);               // insert it
}   // end while
}
for (int i = 0; i < nVerts; i++) {
vertexList[i].wasVisited=false;
}
}

}

public class App {
public static void main(String[] args) {
Graph graph = new Graph();
graph.addVertex('A');
graph.addVertex('B');
graph.addVertex('C');
graph.addVertex('D');
graph.addVertex('E');

graph.addEdge(0,1);
graph.addEdge(1,2);
graph.addEdge(0,3);
graph.addEdge(3,4);
System.out.println("Visits:");
graph.bfs();
System.out.println();
}
}

MST

package org.exam.ch13.mst;

/**
* Created by xin on 15.10.18.
*/
class StackX {
private final int SIZE = 20;
private int[] st;
private int top;
public StackX() {
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 label) {
this.label = label;
}
}

class Graph{
private final int MAX_VERTS=20;
private Vertex[] vertexList;
private int[][] adjMat;
private int nVerts;//默认值为0
private StackX stackX;
public Graph(){
vertexList=new Vertex[MAX_VERTS];//里面元素为空
adjMat=new int[MAX_VERTS][MAX_VERTS];//元素默认值都为0
stackX=new StackX();
}
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 index){
System.out.print(vertexList[index].label);
}
public int getAdjUnvisitedVertex(int v){
for (int i = 0; i < nVerts; i++) {
if (adjMat[v][i]==1&&vertexList[i].wasVisited==false){
return i;
}
}
return -1;
}
public void mst(){
vertexList[0].wasVisited=true;
stackX.push(0);
while (!stackX.isEmpty()){
int curVertex=stackX.peek();
int v=getAdjUnvisitedVertex(curVertex);
if (v==-1){
stackX.pop();
}else{
vertexList[v].wasVisited=true;
displayVertex(curVertex);
displayVertex(v);
System.out.print(" ");
stackX.push(v);
}
}
for (int i = 0; i < nVerts; i++) {
vertexList[i].wasVisited=false;
}
}
}

public class App {
public static void main(String[] args) {
Graph graph = new Graph();
graph.addVertex('A');
graph.addVertex('B');
graph.addVertex('C');
graph.addVertex('D');
graph.addVertex('E');

graph.addEdge(0,1);
graph.addEdge(0,2);
graph.addEdge(0,3);
graph.addEdge(0,4);
graph.addEdge(1,2);
graph.addEdge(1,3);
graph.addEdge(1,4);
graph.addEdge(2,3);
graph.addEdge(2,4);
graph.addEdge(3,4);

System.out.print("Minimum spanning tree: ");
graph.mst(); // minimum spanning tree
System.out.println();
}
}