A星

.classpath

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+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.7"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>

.gitignore

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+/bin/

.project

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+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>A星算法</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

.settings/org.eclipse.jdt.core.prefs

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+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.7
+org.eclipse.jdt.core.compiler.codegen.unusedLocal=preserve
+org.eclipse.jdt.core.compiler.compliance=1.7
+org.eclipse.jdt.core.compiler.debug.lineNumber=generate
+org.eclipse.jdt.core.compiler.debug.localVariable=generate
+org.eclipse.jdt.core.compiler.debug.sourceFile=generate
+org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
+org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
+org.eclipse.jdt.core.compiler.source=1.7

README.md

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+# astar
+A星算法Java实现

src/AStar.java

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+import java.util.ArrayList;
+import java.util.List;
+import java.util.PriorityQueue;
+import java.util.Queue;
+
+/**
+ * 
+ * ClassName: AStar 
+ * @Description: A星算法
+ * @author kesar
+ */
+public class AStar
+{
+	public final static int BAR = 1; // 障碍值
+	public final static int PATH = 2; // 路径
+	public final static int DIRECT_VALUE = 10; // 横竖移动代价
+	public final static int OBLIQUE_VALUE = 14; // 斜移动代价
+
+	/**
+	 * 包含地图所需的所有输入数据
+	 */
+	static class MapInfo
+	{
+		int[][] maps; // 二维数组的地图
+		int width; // 地图的宽
+		int hight; // 地图的高
+		Node start; // 起始结点
+		Node end; // 最终结点
+
+		public MapInfo(int[][] maps, int width, int hight, Node start, Node end)
+		{
+			this.maps = maps;
+			this.width = width;
+			this.hight = hight;
+			this.start = start;
+			this.end = end;
+		}
+	}
+
+	Queue<Node> openList = new PriorityQueue<Node>(); // 优先队列(升序)
+	List<Node> closeList = new ArrayList<Node>();
+
+	public static void main(String[] args)
+	{
+		int[][] maps = { 
+				{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
+				{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
+				{ 0, 0, 8, 8, 0, 0, 0, 0, 0, 0, 8, 8, 8, 0, 0 },
+				{ 0, 0, 0, 8, 0, 0, 0, 0, 0, 8, 8, 0, 0, 0, 0 },
+				{ 0, 0, 0, 8, 0, 0, 0, 0, 8, 8, 0, 0, 0, 0, 0 },
+				{ 0, 0, 0, 8, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0 },
+				{ 0, 0, 0, 8, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0 } 
+				};
+		MapInfo info=new MapInfo(maps,maps[0].length, maps.length,new Node(1, 5), new Node(10, 5));
+		new AStar().start(info);
+		printMap(maps);
+	}
+
+	/**
+	 * 打印地图
+	 */
+	public static void printMap(int[][] maps)
+	{
+		for (int i = 0; i < maps.length; i++)
+		{
+			for (int j = 0; j < maps[i].length; j++)
+			{
+				System.out.print(maps[i][j] + " ");
+			}
+			System.out.println();
+		}
+	}
+
+	/**
+	 * 开始算法
+	 */
+	public void start(MapInfo mapInfo)
+	{
+		if(mapInfo==null) return;
+		// clean
+		openList.clear();
+		closeList.clear();
+		// 开始搜索
+		openList.add(mapInfo.start);
+		moveNodes(mapInfo);
+	}
+
+	/**
+	 * 移动当前结点
+	 */
+	private void moveNodes(MapInfo mapInfo)
+	{
+		while (!openList.isEmpty())
+		{
+			if (isCoordInClose(mapInfo.end.coord))
+			{
+				drawPath(mapInfo.maps, mapInfo.end);
+				break;
+			}
+			Node current = openList.poll();
+			closeList.add(current);
+			addNeighborNodeInOpen(mapInfo,current);
+		}
+	}
+
+	/**
+	 * 在二维数组中绘制路径
+	 */
+	private void drawPath(int[][] maps, Node end)
+	{
+		if(end==null||maps==null) return;
+		System.out.println("总代价：" + end.G);
+		while (end != null)
+		{
+			Coord c = end.coord;
+			maps[c.y][c.x] = PATH;
+			end = end.parent;
+		}
+	}
+
+	/**
+	 * 添加所有邻结点到open表
+	 */
+	private void addNeighborNodeInOpen(MapInfo mapInfo,Node current)
+	{
+		int x = current.coord.x;
+		int y = current.coord.y;
+		// 左
+		addNeighborNodeInOpen(mapInfo,current, x - 1, y, DIRECT_VALUE);
+		// 上
+		addNeighborNodeInOpen(mapInfo,current, x, y - 1, DIRECT_VALUE);
+		// 右
+		addNeighborNodeInOpen(mapInfo,current, x + 1, y, DIRECT_VALUE);
+		// 下
+		addNeighborNodeInOpen(mapInfo,current, x, y + 1, DIRECT_VALUE);
+		// 左上
+		addNeighborNodeInOpen(mapInfo,current, x - 1, y - 1, OBLIQUE_VALUE);
+		// 右上
+		addNeighborNodeInOpen(mapInfo,current, x + 1, y - 1, OBLIQUE_VALUE);
+		// 右下
+		addNeighborNodeInOpen(mapInfo,current, x + 1, y + 1, OBLIQUE_VALUE);
+		// 左下
+		addNeighborNodeInOpen(mapInfo,current, x - 1, y + 1, OBLIQUE_VALUE);
+	}
+
+	/**
+	 * 添加一个邻结点到open表
+	 */
+	private void addNeighborNodeInOpen(MapInfo mapInfo,Node current, int x, int y, int value)
+	{
+		if (canAddNodeToOpen(mapInfo,x, y))
+		{
+			Node end=mapInfo.end;
+			Coord coord = new Coord(x, y);
+			int G = current.G + value; // 计算邻结点的G值
+			Node child = findNodeInOpen(coord);
+			if (child == null)
+			{
+				int H=calcH(end.coord,coord); // 计算H值
+				if(isEndNode(end.coord,coord))
+				{
+					child=end;
+					child.parent=current;
+					child.G=G;
+					child.H=H;
+				}
+				else
+				{
+					child = new Node(coord, current, G, H);
+				}
+				openList.add(child);
+			}
+			else if (child.G > G)
+			{
+				child.G = G;
+				child.parent = current;
+				openList.add(child);
+			}
+		}
+	}
+
+	/**
+	 * 从Open列表中查找结点
+	 */
+	private Node findNodeInOpen(Coord coord)
+	{
+		if (coord == null || openList.isEmpty()) return null;
+		for (Node node : openList)
+		{
+			if (node.coord.equals(coord))
+			{
+				return node;
+			}
+		}
+		return null;
+	}
+
+
+	/**
+	 * 计算H的估值：“曼哈顿”法，坐标分别取差值相加
+	 */
+	private int calcH(Coord end,Coord coord)
+	{
+		return Math.abs(end.x - coord.x)
+				+ Math.abs(end.y - coord.y);
+	}
+
+	/**
+	 * 判断结点是否是最终结点
+	 */
+	private boolean isEndNode(Coord end,Coord coord)
+	{
+		return coord != null && end.equals(coord);
+	}
+
+	/**
+	 * 判断结点能否放入Open列表
+	 */
+	private boolean canAddNodeToOpen(MapInfo mapInfo,int x, int y)
+	{
+		// 是否在地图中
+		if (x < 0 || x >= mapInfo.width || y < 0 || y >= mapInfo.hight) return false;
+		// 判断是否是不可通过的结点
+		if (mapInfo.maps[y][x] == BAR) return false;
+		// 判断结点是否存在close表
+		if (isCoordInClose(x, y)) return false;
+
+		return true;
+	}
+
+	/**
+	 * 判断坐标是否在close表中
+	 */
+	private boolean isCoordInClose(Coord coord)
+	{
+		return coord!=null&&isCoordInClose(coord.x, coord.y);
+	}
+
+	/**
+	 * 判断坐标是否在close表中
+	 */
+	private boolean isCoordInClose(int x, int y)
+	{
+		if (closeList.isEmpty()) return false;
+		for (Node node : closeList)
+		{
+			if (node.coord.x == x && node.coord.y == y)
+			{
+				return true;
+			}
+		}
+		return false;
+	}
+}

src/Coord.java

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+/**
+ * 
+ * ClassName: Coord
+ * 
+ * @Description: 坐标
+ * @author kesar
+ */
+public class Coord
+{
+
+	public int x;
+	public int y;
+
+	public Coord(int x, int y)
+	{
+		this.x = x;
+		this.y = y;
+	}
+
+	@Override
+	public boolean equals(Object obj)
+	{
+		if (obj == null) return false;
+		if (obj instanceof Coord)
+		{
+			Coord c = (Coord) obj;
+			return x == c.x && y == c.y;
+		}
+		return false;
+	}
+
+	@Override
+	public String toString()
+	{
+		return "Coord [x=" + x + ", y=" + y + "]";
+	}
+}

src/Node.java

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+/**
+ * 
+ * ClassName: Node 
+ * 
+ * @Description: 路径结点
+ * @author kesar
+ */
+public class Node implements Comparable<Node>
+{
+
+	public Coord coord; // 坐标
+	public Node parent; // 父结点
+	public int G; // G：是个准确的值，是起点到当前结点的代价
+	public int H; // H：是个估值，当前结点到目的结点的估计代价
+
+	public Node(int x, int y)
+	{
+		this.coord = new Coord(x, y);
+	}
+
+	public Node(Coord coord, Node parent, int g, int h)
+	{
+		this.coord = coord;
+		this.parent = parent;
+		G = g;
+		H = h;
+	}
+
+	@Override
+	public int compareTo(Node o)
+	{
+		if (o == null) return -1;
+		if (G + H > o.G + o.H)
+			return 1;
+		else if (G + H < o.G + o.H) return -1;
+		return 0;
+	}
+
+	@Override
+	public String toString()
+	{
+		return "Node [coord=" + coord + "]";
+	}
+
+}