AStar

来源：互联网发布：js新建窗口打印带图片编辑：程序博客网时间：2024/05/17 02:32

以前对A*算法的理解停留在人工智能书本上面，但是最近2天看了Stanford的一个游戏介绍网站http://theory.stanford.edu/~amitp/GameProgramming/之后，觉得对A*算法有了比较深刻的了解。那个网站对A*描述没有课本1条又1条的公式化，更多的是图形，结合游戏本身实际来描述，觉得帮助很大。

现在用Java编写了一个算法演示，效果还不错，不过现在open列表是链表形式，效率o(n)比较差，下一步可以考虑用堆插入查找来实现o(lgn)(不过其实现在100×100看起来还可以吧，暂时没有什么动力做，看以后需要吧）

附：算法源代码，不妥之处，还望各位指正。

AStar.java（算法核心）

/**

package Arithmetic;

import java.util.*;

import GUI.*;

/**

* @author 冯家耀

public class AStar {

final int BARRIER = -3;

final int START = -1;

final int END = -2;

Node [][]grid;

List<Node> open = new LinkedList();

Set close = new HashSet();

Node startNode;

Node endNode;

int [][]result;//1:找过 2:找到 0：空

final int EVEN_FIND = 1;

final int SUC_FIND = 2;

final int NOT_FIND = 0;

int gridRows;

int gridCols;

int D = 1;

public AStar(GridValue [][]g){

if(g==null)return;

gridRows = g.length;

gridCols = g[0].length;

grid = new Node[gridRows][gridCols];

result = new int[gridRows][gridCols];

boolean hasfindfirst = false;

boolean hasfindend = false;

for(int i=0;i<gridRows;i++){

for(int j = 0; j < gridCols; j++){

grid[i][j] = new Node(i,j,g[i][j].toInt());

if(! hasfindfirst){

if(grid[i][j].cost == START){

hasfindfirst = true;

startNode = grid[i][j];

}

if(! hasfindend){

if(grid[i][j].cost == END){

hasfindend = true;

endNode = grid[i][j];

}

class Node{

Node parent;

int row;

int col;

int cost;

int f;

int g;

public Node(int row,int col, int cost){

this.row = row;

this.col = col;

this.cost = cost;

}

@Override

public boolean equals(Object obj) {

if(obj instanceof Node && ((Node)obj).row == row && ((Node)obj).col == col)return true;

else return false;

}

@Override

public int hashCode() {

return row*gridCols+col;

}

int estimateH(Node node){

//return D*( (Math.abs(node.row) - endNode.row) + Math.abs(node.col - endNode.col) );

//return D*( Math.max((Math.abs(node.row) - endNode.row) , Math.abs(node.col - endNode.col)) );

int deltay = node.row - endNode.row;

int deltax = node.col - endNode.col;

return (int)(D*Math.sqrt((deltay*deltay + deltax*deltax)));

}

public boolean findPath(){

insertIntoOpen(startNode);

while(!open.isEmpty()){

Node node = open.remove(0);

System.out.println("Scan open");

result[node.row][node.col] = EVEN_FIND;

if(node.equals(endNode)){

markEven(node);

createPath();

return true;

}

else{

List neighborNodeList = findNeighbor(node);

Iterator<Node> it = neighborNodeList.iterator();

while(it.hasNext()){

Node neighborNode = it.next();

if(close.contains(neighborNode)){

continue;

}

else{//FIXME 效率超低

if(! open.contains(neighborNode)){

neighborNode.g = node.g + neighborNode.cost;

neighborNode.f = neighborNode.g + estimateH(neighborNode);

neighborNode.parent = node;

insertIntoOpen(neighborNode);

}

else{

if(node.g + neighborNode.cost + estimateH(neighborNode) < neighborNode.f){

neighborNode.g = node.g + neighborNode.cost;

neighborNode.f = neighborNode.g + estimateH(neighborNode);

open.remove(neighborNode);

neighborNode.parent = node;

insertIntoOpen(neighborNode);

}

close.add(node);

}

return false;

}

private void markEven(Node node){

result[node.row][node.col] = -1;

}

private void createPath(){

LinkedList pathlist = new LinkedList();

Node tmp = endNode;

while(tmp.parent != null){

result[tmp.row][tmp.col] = SUC_FIND;

tmp = tmp.parent;

}

private List findNeighbor(Node node){

List<Node> list = new ArrayList();

int left = node.col-1;

int up = node.row-1;

int down = node.row+1;

int right = node.col+1;

if(left > 0){

if(grid[node.row][left].cost != BARRIER)

list.add(grid[node.row][left]);

if(up>0){

if(grid[up][node.col].cost != BARRIER)

list.add(grid[up][node.col]);

if(grid[up][left].cost != BARRIER)

list.add(grid[up][left]);

}

if(down < gridRows - 1){

if(grid[down][node.col].cost != BARRIER)

list.add(grid[down][node.col]);

if(grid[down][left].cost != BARRIER)

list.add(grid[down][left]);

}

if(right < gridCols - 1){

if(grid[node.row][right].cost != BARRIER)

list.add(grid[node.row][right]);

if(up>0){

if(grid[up][right].cost != BARRIER)

list.add(grid[up][right]);

}

if( down < gridRows - 1){

if(grid[down][right].cost != BARRIER)

list.add(grid[down][right]);

}

return list;

}

public int[][] getResult(){

return result;

}

private void insertIntoOpen(Node node){

int size = open.size();

Iterator<Node>it = open.iterator();

int i = 0;

while(it.hasNext()){

if(it.next().f > node.f)break;

i++;

}

open.add(i, node);

System.out.println("OPEN ADD NODE:("+ node.row+","+node.col+")" );

}

GridValue.java

package GUI;

public enum GridValue{

BARRIER(-3),

START(-1),

END(-2),

LEN1(1),

LEN10(10),

LEN50(50),

LEN100(100),

LEN150(150);

private int value;

private GridValue(int value){

this.value = value;

}

public int toInt(){

return this.value;

}

MainForm.java（界面展示）

package GUI;

import java.awt.*;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.event.MouseAdapter;

import java.awt.event.MouseEvent;

import javax.swing.BoxLayout;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JOptionPane;

import javax.swing.JPanel;

import javax.swing.JSplitPane;

import javax.swing.WindowConstants;

import sun.font.GlyphLayout.GVData;

/**

* This code was edited or generated using CloudGarden's Jigloo

* SWT/Swing GUI Builder, which is free for non-commercial

* use. If Jigloo is being used commercially (ie, by a corporation,

* company or business for any purpose whatever) then you

* should purchase a license for each developer using Jigloo.

* Please visit www.cloudgarden.com for details.

* Use of Jigloo implies acceptance of these licensing terms.

* A COMMERCIAL LICENSE HAS NOT BEEN PURCHASED FOR

* THIS MACHINE, SO JIGLOO OR THIS CODE CANNOT BE USED

* LEGALLY FOR ANY CORPORATE OR COMMERCIAL PURPOSE.

public class MainForm extends javax.swing.JFrame {

private JSplitPane jSplitPane1;

private JButton jButton3;

private JButton jButton2;

private JButton jButton1;

private JPanel jPanel17;

private JPanel jPanel1;

private JLabel jLabel3;

private JLabel jLabel4;

private JLabel jLabel5;

private JPanel jPanel1Start;

private JLabel jLabel7;

private JPanel jPanel1End;

private JPanel jPanel14;

private JPanel jPanel16;

private JLabel jLabel6;

private JPanel jPanel12;

private JPanel jPanel1Barrier;

private JPanel jPanel10;

private JPanel jPanelLength150;

private JPanel jPanel8;

private JPanel jPanelLength100;

private JPanel jPanel6;

private JLabel jLabel2;

private JPanel jPanelLength50;

private JPanel jPanel4;

private JLabel jLabel1;

private JPanel jPanelLength10;

private GridPanel gridPanel;

private JPanel jPanel2;

/**

* Auto-generated main method to display this JFrame

public static void main(String[] args) {

MainForm inst = new MainForm();

inst.setVisible(true);

inst.setTitle("A*算法演示");

}

public MainForm() {

super();

initGUI();

}

private void initGUI() {

try {

setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);

{

jSplitPane1 = new JSplitPane();

getContentPane().add(jSplitPane1, BorderLayout.CENTER);

jSplitPane1.setDividerSize(1);

jSplitPane1.setDividerLocation(412);

jSplitPane1.setResizeWeight(1.0);

{

gridPanel = new GridPanel();

gridPanel.setBackground(Color.BLACK);

gridPanel.setPreferredSize(new Dimension(411,411));

jSplitPane1.setLeftComponent(gridPanel);

// gridPanel.addMouseListener(new )

}

{

jPanel2 = new JPanel();

FlowLayout jPanel2Layout = new FlowLayout();

jPanel2Layout.setAlignment(FlowLayout.LEFT);

jSplitPane1.setRightComponent(jPanel2);

jPanel2.setBackground(Color.GRAY);

jPanel2.setPreferredSize(new Dimension(40,400));

jPanel2.setLayout(jPanel2Layout);

{

jPanel1 = new JPanel();

FlowLayout jPanel1Layout = new FlowLayout();

jPanel1Layout.setAlignment(FlowLayout.LEFT);

jPanel1.setLayout(jPanel1Layout);

jPanel2.add(jPanel1);

jPanel1.setPreferredSize(new java.awt.Dimension(165,26));

jPanel1.setBackground(new java.awt.Color(128,128,128));

{

jPanelLength10 = new JPanel();

jPanel1.add(jPanelLength10);

GridLayout jPanel3Layout = new GridLayout(1, 1);

jPanel3Layout.setHgap(5);

jPanel3Layout.setVgap(5);

jPanel3Layout.setColumns(1);

jPanelLength10.setLayout(jPanel3Layout);

jPanelLength10.setPreferredSize(new java.awt.Dimension(15, 13));

jPanelLength10.setBackground(new java.awt.Color(33,233,0));

jPanelLength10.addMouseListener(new MouseAdapter() {

public void mousePressed(MouseEvent evt) {

gridPanel.setCurrentValue(GridValue.LEN10);

}

});

}

{

jLabel1 = new JLabel();

jPanel1.add(jLabel1);

jLabel1.setText("10");

}

{

jPanel4 = new JPanel();

FlowLayout jPanel4Layout = new FlowLayout();

jPanel4Layout.setAlignment(FlowLayout.LEFT);

jPanel4.setLayout(jPanel4Layout);

jPanel2.add(jPanel4);

jPanel4.setPreferredSize(new java.awt.Dimension(165,26));

jPanel4.setBackground(new java.awt.Color(128,128,128));

{

jPanelLength50 = new JPanel();

GridLayout jPanel5Layout = new GridLayout(1, 1);

jPanel5Layout.setHgap(5);

jPanel5Layout.setVgap(5);

jPanel5Layout.setColumns(1);

jPanel4.add(jPanelLength50);

jPanelLength50.setBackground(new java.awt.Color(255,128,128));

jPanelLength50.setPreferredSize(new java.awt.Dimension(15,13));

jPanelLength50.setLayout(jPanel5Layout);

jPanelLength50.addMouseListener(new MouseAdapter() {

public void mousePressed(MouseEvent evt) {

gridPanel.setCurrentValue(GridValue.LEN50);

}

});

}

{

jLabel2 = new JLabel();

jPanel4.add(jLabel2);

jLabel2.setText("50");

}

{

jPanel6 = new JPanel();

jPanel2.add(jPanel6);

FlowLayout jPanel6Layout = new FlowLayout();

jPanel6Layout.setAlignment(FlowLayout.LEFT);

jPanel6.setLayout(jPanel6Layout);

jPanel6.setPreferredSize(new java.awt.Dimension(165,26));

jPanel6.setBackground(new java.awt.Color(128,128,128));

{

jPanelLength100 = new JPanel();

GridLayout jPanel7Layout = new GridLayout(1, 1);

jPanel7Layout.setHgap(5);

jPanel7Layout.setVgap(5);

jPanel7Layout.setColumns(1);

jPanel6.add(jPanelLength100);

jPanelLength100.setBackground(new java.awt.Color(255,255,128));

jPanelLength100.setPreferredSize(new java.awt.Dimension(15,13));

jPanelLength100.setLayout(jPanel7Layout);

jPanelLength100

.addMouseListener(new MouseAdapter() {

public void mousePressed(MouseEvent evt) {

gridPanel.setCurrentValue(GridValue.LEN100);

}

});

}

{

jLabel3 = new JLabel();

jPanel6.add(jLabel3);

jLabel3.setText("100");

}

{

jPanel8 = new JPanel();

FlowLayout jPanel8Layout = new FlowLayout();

jPanel8Layout.setAlignment(FlowLayout.LEFT);

jPanel8.setLayout(jPanel8Layout);

jPanel2.add(jPanel8);

jPanel8.setPreferredSize(new java.awt.Dimension(165,26));

jPanel8.setBackground(new java.awt.Color(128,128,128));

{

jPanelLength150 = new JPanel();

GridLayout jPanel9Layout = new GridLayout(1, 1);

jPanel9Layout.setHgap(5);

jPanel9Layout.setVgap(5);

jPanel9Layout.setColumns(1);

jPanel8.add(jPanelLength150);

jPanelLength150.setBackground(new java.awt.Color(128,255,128));

jPanelLength150.setPreferredSize(new java.awt.Dimension(15,13));

jPanelLength150.setLayout(jPanel9Layout);

jPanelLength150

.addMouseListener(new MouseAdapter() {

public void mousePressed(MouseEvent evt) {

gridPanel.setCurrentValue(GridValue.LEN150);

}

});

}

{

jLabel4 = new JLabel();

jPanel8.add(jLabel4);

jLabel4.setText("150");

}

{

jPanel10 = new JPanel();

FlowLayout jPanel10Layout = new FlowLayout();

jPanel10Layout.setAlignment(FlowLayout.LEFT);

jPanel10.setLayout(jPanel10Layout);

jPanel2.add(jPanel10);

jPanel10.setPreferredSize(new java.awt.Dimension(165,26));

jPanel10.setBackground(new java.awt.Color(128,128,128));

{

jPanel1Barrier = new JPanel();

GridLayout jPanel11Layout = new GridLayout(1, 1);

jPanel11Layout.setHgap(5);

jPanel11Layout.setVgap(5);

jPanel11Layout.setColumns(1);

jPanel10.add(jPanel1Barrier);

jPanel1Barrier.setBackground(new java.awt.Color(128,255,255));

jPanel1Barrier.setPreferredSize(new java.awt.Dimension(15,13));

jPanel1Barrier.setLayout(jPanel11Layout);

jPanel1Barrier.addMouseListener(new MouseAdapter() {

public void mousePressed(MouseEvent evt) {

gridPanel.setCurrentValue(GridValue.BARRIER);

}

});

}

{

jLabel5 = new JLabel();

jPanel10.add(jLabel5);

jLabel5.setText("固体");

}

{

jPanel12 = new JPanel();

FlowLayout jPanel12Layout = new FlowLayout();

jPanel12Layout.setAlignment(FlowLayout.LEFT);

jPanel12.setLayout(jPanel12Layout);

jPanel2.add(jPanel12);

jPanel12.setPreferredSize(new java.awt.Dimension(165,26));

jPanel12.setBackground(new java.awt.Color(128,128,128));

{

jPanel1Start = new JPanel();

GridLayout jPanel13Layout = new GridLayout(1, 1);

jPanel13Layout.setHgap(5);

jPanel13Layout.setVgap(5);

jPanel13Layout.setColumns(1);

jPanel12.add(jPanel1Start);

jPanel1Start.setBackground(new java.awt.Color(255,0,255));

jPanel1Start.setPreferredSize(new java.awt.Dimension(15,13));

jPanel1Start.setLayout(jPanel13Layout);

jPanel1Start.addMouseListener(new MouseAdapter() {

public void mouseClicked(MouseEvent evt) {

gridPanel.setCurrentValue(GridValue.START);

}

});

}

{

jLabel6 = new JLabel();

jPanel12.add(jLabel6);

jLabel6.setText("起点");

}

{

jPanel16 = new JPanel();

jPanel2.add(jPanel16);

jPanel16.setBackground(new java.awt.Color(128,128,128));

jPanel16.setPreferredSize(new java.awt.Dimension(165,26));

{

jPanel14 = new JPanel();

FlowLayout jPanel14Layout = new FlowLayout();

jPanel14Layout.setAlignment(FlowLayout.LEFT);

jPanel14.setLayout(jPanel14Layout);

jPanel16.add(jPanel14);

jPanel14.setBackground(new java.awt.Color(

128,

128));

jPanel14.setPreferredSize(new java.awt.Dimension(

165,

26));

{

jPanel1End = new JPanel();

GridLayout jPanel15Layout = new GridLayout(1, 1);

jPanel15Layout.setHgap(5);

jPanel15Layout.setVgap(5);

jPanel15Layout.setColumns(1);

jPanel14.add(jPanel1End);

jPanel1End.setBackground(new java.awt.Color(128,0,255));

jPanel1End.setPreferredSize(new java.awt.Dimension(15,13));

jPanel1End.setLayout(jPanel15Layout);

jPanel1End.addMouseListener(new MouseAdapter() {

public void mouseClicked(MouseEvent evt) {

gridPanel.setCurrentValue(GridValue.END);

}

});

}

{

jLabel7 = new JLabel();

jPanel14.add(jLabel7);

jLabel7.setText("终点");

}

{

jPanel17 = new JPanel();

GridBagLayout jPanel17Layout = new GridBagLayout();

jPanel17Layout.rowWeights = new double[] {0.1, 0.0, 0.0};

jPanel17Layout.rowHeights = new int[] {7, 35, 35};

jPanel17Layout.columnWeights = new double[] {0.1};

jPanel17Layout.columnWidths = new int[] {7};

jPanel17.setLayout(jPanel17Layout);

jPanel2.add(jPanel17);

jPanel17.setPreferredSize(new java.awt.Dimension(170, 197));

jPanel17.setBackground(new java.awt.Color(128,128,128));

{

jButton1 = new JButton();

jPanel17.add(jButton1, new GridBagConstraints(0, 1, 1, 1, 0.0, 0.0, GridBagConstraints.CENTER, GridBagConstraints.NONE, new Insets(0, 0, 0, 0), 0, 0));

jButton1.setText("计算");

jButton1.setPreferredSize(new java.awt.Dimension(130, 25));

jButton1.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent evt) {

Arithmetic.AStar astar = new Arithmetic.AStar(gridPanel.getGrid());

if(

astar.findPath()

){

gridPanel.setResult(astar.getResult());

JOptionPane.showConfirmDialog(MainForm.this, "FOUND");

}

else JOptionPane.showConfirmDialog(MainForm.this, "NOT FOUND");

gridPanel.repaint();

}

});

}

{

jButton2 = new JButton();

jPanel17.add(jButton2, new GridBagConstraints(0, 2, 2, 1, 0.0, 0.0, GridBagConstraints.CENTER, GridBagConstraints.NONE, new Insets(0, 0, 0, 0), 0, 0));

jButton2.setText("消除路径");

jButton2.setPreferredSize(new java.awt.Dimension(130, 25));

jButton2.addMouseListener(new MouseAdapter() {

public void mouseClicked(MouseEvent evt) {

System.out

.println("jButton2.mouseClicked, event="

+ evt);

//TODO add your code for jButton2.mouseClicked

}

});

}

{

jButton3 = new JButton();

jPanel17.add(jButton3, new GridBagConstraints(0, 0, 1, 1, 0.0, 0.0, GridBagConstraints.CENTER, GridBagConstraints.NONE, new Insets(0, 0, 0, 0), 0, 0));

jButton3.setText("清空所有");

jButton3.setPreferredSize(new java.awt.Dimension(130,25));

jButton3.addMouseListener(new MouseAdapter() {

public void mouseClicked(MouseEvent evt) {

gridPanel.clearAll();

gridPanel.setResult(null);

gridPanel.repaint();

}

});

}

pack();

this.setSize(600, 450);

//this.setExtendedState(JFrame.MAXIMIZED_BOTH);

} catch (Exception e) {

e.printStackTrace();

}

@Override

public void paint(Graphics g) {

// TODO 自动生成方法存根

super.paint(g);

}

class GridPanel extends JPanel{

final int rows = 20;

final int cols = 20;

GridValue [][]grid = new GridValue[rows][cols];

final int gridPanelWidth = 411;

final int gridPanelHeight = 411;

int [][]result;

int rowspan = (gridPanelHeight - 10 - 1) / rows;

int colspan = (gridPanelWidth - 10 - 1) / cols;

int edge = 5;

private GridValue currentValue = GridValue.LEN1;

public GridPanel() {

for(int i = 0; i < rows; i++)

for(int j = 0; j < cols;j++){

grid[i][j] = GridValue.LEN1;

}

addMouseListener(new MouseAdapter(){

@Override

public void mousePressed(MouseEvent e) {

int xgrid = (e.getX() - edge) / colspan;

int ygrid = (e.getY() - edge) / rowspan;

grid[ygrid][xgrid] = currentValue;

repaint();

}

});

}

public GridValue[][] getGrid(){

return grid;

}

public void setResult(int[][]result){

this.result = result;

}

public void clearAll(){

for(int i = 0; i < rows; i++){

for(int j = 0; j < cols;j++){

grid[i][j] = GridValue.LEN1;

}

repaint();

}

public void setCurrentValue(GridValue value){

currentValue = value;

}

public void drawGrid(Graphics g,int row,int col){

//grid[row][col] = value;

int startrow = edge + rowspan*row;

int startcol = edge + colspan*col;

boolean draw = true;

switch(grid[row][col]){

case BARRIER:

g.setColor(new java.awt.Color(128,255,255));

break;

case START:

g.setColor(new java.awt.Color(255,0,255));

break;

case END:

g.setColor(new java.awt.Color(128,0,255));

break;

case LEN1:

draw = false;

break;

case LEN10:

g.setColor(new java.awt.Color(33,233,0));

break;

case LEN50:

g.setColor(new java.awt.Color(255,128,128));

break;

case LEN100:

g.setColor(new java.awt.Color(255,255,128));

break;

case LEN150:

g.setColor(new java.awt.Color(128,255,128));

break;

default:break;

}

if(draw)

g.fillRect(startcol + colspan/4, startrow+rowspan/4, rowspan/2, colspan/2);

}

public void drawResult(Graphics g,int row,int col){

if(result == null)return;

int startrow = edge + rowspan*row;

int startcol = edge + colspan*col;

int r = result[row][col];

boolean draw = true;

if(r == 0)return;

if(r == 1)g.setColor(Color.WHITE);

if(r == 2)g.setColor(Color.YELLOW);

g.drawOval(startcol + colspan/2, startrow+rowspan/2, colspan/4, rowspan/4);

}

@Override

public void paint(Graphics g) {

super.paint(g);

g.setColor(Color.WHITE);

for(int i = 0;i < rows+1;i++){

g.drawLine(edge, edge + rowspan*i, gridPanelWidth - edge - 1, edge + rowspan*i);

}

for(int i = 0;i < cols+1;i++){

g.drawLine( edge + colspan*i, edge, edge + colspan*i, gridPanelHeight - edge - 1);

}

for(int i = 0; i < rows; i++){

for(int j = 0; j < cols;j++){

drawGrid(g, i, j);

drawResult(g,i,j);

}