import java.util.ArrayList; // A*算法寻路
public class AStar2 {
public static final int[][] maps = {
{0, 0, 0, 1, 0, 0, 0, 0, 0},
{0, 0, 0, 1, 0, 0, 0, 0, 0},
{0, 0, 0, 1, 0, 0, 0, 0, 0},
{0, 0, 0, 1, 0, 0, 0, 0, 0},
{0, 0, 0, 1, 0, 0, 0, 0, 0},
{0, 0, 0, 1, 0, 0, 0, 0, 0},
{0, 0, 0, 1, 0, 0, 0, 0, 0},
{0, 0, 0, 1, 0, 0, 0, 0, 0},
{0, 0, 0, 0, 0, 0, 0, 0, 0},
}; public static int straight = 10;
public static int diagonal = 14; // 开放列表
public static ArrayList<Node> openList = new ArrayList<>();
// 闭合列表
public static ArrayList<Node> colseList = new ArrayList<>();
// 方向
public static int[][] direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}, {1, 1}, {1, -1}, {-1, 1}, {-1, -1}}; public static void main(String[] args) {
//定点:起点终点
Node start = new Node(5, 1);
Node end = new Node(5, 4); Node endNode = findPath(start, end); printMap(maps, start, end); ArrayList<Node> arrayList = endNode != null ? getPaths(endNode) : null; printPaths(arrayList); } // 从起点开始，找到到终点的一条最短路径
private static Node findPath(Node start, Node end) {
start.G = 0;
openList.add(start); while (!openList.isEmpty()) {
//从开放列表中拿到最小F节点
Node cureNode = minFINOpenList(openList);
openList.remove(cureNode);
// 将该节点加入到闭合列表中
colseList.add(cureNode); // 当前节点的全部合法邻居
ArrayList<Node> neighbors = getNeighbor(cureNode);
for (Node nbrNode : neighbors) {
// 邻居已经在openList
if (exists(openList, nbrNode) != null)
updateG(cureNode, nbrNode);
// 邻居不在openList
else joinOpenList(cureNode, nbrNode, end);
}
if (exists(openList, end) != null)
return exists(openList, end);
} return null;
} private static ArrayList<Node> getPaths(Node endNode) {
ArrayList<Node> arrayList = new ArrayList<>();
Node parent = endNode;
while (parent != null) {
arrayList.add(parent);
parent = parent.parent;
}
return arrayList;
} private static int calStep(Node node, Node cur) {
if (inLine(node, cur))
return straight;
else return diagonal;
} private static int calH(Node endNode, Node nbrNode) {
return Math.abs(endNode.y - nbrNode.y) + Math.abs(endNode.x - nbrNode.x);
} // 计算距离起点的距离
private static int calG(Node cureNode, Node nbrNode) {
int step = calStep(cureNode, nbrNode);
return cureNode.G + step;
} private static boolean inLine(Node nbr, Node cur) {
if (nbr.x == cur.x || nbr.y == cur.y)
return true;
return false;
} // 途径当前节点到达节点node的路径G会不会更短
private static void updateG(Node cureNode, Node nbrNode) {
int step = calStep(cureNode, nbrNode);
int G = calG(cureNode, nbrNode);
if (G < nbrNode.G) {
nbrNode.G = G;
nbrNode.parent = cureNode;
nbrNode.calcF();
}
} private static void joinOpenList(Node curNode, Node nbrNode, Node endNode) {
openList.add(nbrNode);
nbrNode.parent = curNode;
nbrNode.G = calG(curNode, nbrNode);
nbrNode.H = calH(endNode, nbrNode);
nbrNode.calcF();
} // 达到当前节点的可达，且不在closeList中的邻居节点
private static ArrayList<Node> getNeighbor(Node cureNode) {
ArrayList<Node> arrayList = new ArrayList<>();
//从当前节点想八个方向扩散
for (int i = 0; i < 8; i++) {
int newRow = cureNode.x + direct[i][0];
int newCol = cureNode.y + direct[i][1];
//当前邻居节点: 可达、不在closeList中
if (isAccesse(newRow, newCol) && !exists(colseList, newRow, newCol)) {
arrayList.add(new Node(newRow, newCol));
}
}
return arrayList;
} private static Node exists(ArrayList<Node> colseList, Node cur) {
for (Node node : colseList) {
if (node.x == cur.x && node.y == cur.y)
return node;
}
return null;
} private static boolean exists(ArrayList<Node> colseList, int newX, int newY) {
for (Node node : colseList) {
if (node.x == newX && node.y == newY)
return true;
}
return false;
} // 可达性分析(非障碍物)
private static boolean isAccesse(int newX, int newY) {
if (0 <= newX && newX < maps.length && 0 <= newY && newY < maps[0].length)
return maps[newX][newY] == 0;
return false;
} // 从开放列表中找到最小F=G+H的节点
private static Node minFINOpenList(ArrayList<Node> openList) {
Node min = openList.get(0);
for (Node node : openList) {
if (node.F < min.F)
min = node;
}
return min;
} private static void printMap(int[][] maps, Node start, Node end) { for (int col = 0; col < maps[0].length; col++) {
System.out.print("\t" + col + "");
}
System.out.print("\n-----------------------------------------\n");
int count = 0;
for (int row = 0; row < maps.length; row++) {
for (int col = 0; col < maps[0].length; col++) {
if (col == 0)
System.out.print(count++ + "|\t");
if (row == start.x && col == start.y || row == end.x && col == end.y)
System.out.print("X\t");
else
System.out.print(maps[row][col] + "\t");
}
System.out.println();
}
System.out.println();
} public static void printPaths(ArrayList<Node> arrayList) {
if (arrayList == null) {
System.out.println("无路可走");
return;
} // 地图形式
for (int col = 0; col < maps[0].length; col++) {
System.out.print("\t" + col + "");
}
System.out.print("\n-----------------------------------------\n");
int count = 0; for (int row = 0; row < maps.length; row++) {
for (int col = 0; col < maps[0].length; col++) {
if (col == 0)
System.out.print(count++ + "|\t");
if (exists(arrayList, row, col)) {
System.out.print("X\t");
} else {
System.out.print(maps[row][col] + "\t");
} }
System.out.println();
}
System.out.println();
// 路径形式
for (int i = arrayList.size() - 1; i >= 0; i--) {
if (i == 0)
System.out.print(arrayList.get(i));
else
System.out.print(arrayList.get(i) + "->");
}
System.out.println();
} }
结果
0 1 2 3 4 5 6 7 8
-----------------------------------------
0| 0 0 0 0 0 0 0 0 0
1| 0 0 0 0 0 0 0 0 0
2| 0 0 0 0 0 0 0 0 0
3| 0 0 0 1 0 0 0 0 0
4| 0 0 0 1 0 0 0 0 0
5| 0 X 0 1 X 0 0 0 0
6| 0 0 0 1 0 0 0 0 0
7| 0 0 0 1 0 0 0 0 0
8| 0 0 0 1 0 0 0 0 0 0 1 2 3 4 5 6 7 8
-----------------------------------------
0| 0 0 0 0 0 0 0 0 0
1| 0 0 0 0 0 0 0 0 0
2| 0 0 0 X 0 0 0 0 0
3| 0 0 X 1 X 0 0 0 0
4| 0 X 0 1 X 0 0 0 0
5| 0 X 0 1 X 0 0 0 0
6| 0 0 0 1 0 0 0 0 0
7| 0 0 0 1 0 0 0 0 0
8| 0 0 0 1 0 0 0 0 0 (5,1)->(4,1)->(3,2)->(2,3)->(3,4)->(4,4)->(5,4)
0 1 2 3 4 5 6 7 8
-----------------------------------------
0| 0 0 0 0 0 0 0 0 0
1| 0 0 0 0 0 0 0 0 0
2| 0 0 0 0 0 0 0 0 0
3| 0 0 0 1 0 0 0 0 0
4| 0 0 0 1 0 0 0 0 0
5| 0 X 0 0 X 0 0 0 0
6| 0 0 0 0 0 0 0 0 0
7| 0 0 0 1 0 0 0 0 0
8| 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8
-----------------------------------------
0| 0 0 0 0 0 0 0 0 0
1| 0 0 0 0 0 0 0 0 0
2| 0 0 0 0 0 0 0 0 0
3| 0 0 0 1 0 0 0 0 0
4| 0 0 0 1 0 0 0 0 0
5| 0 X X X X 0 0 0 0
6| 0 0 0 0 0 0 0 0 0
7| 0 0 0 1 0 0 0 0 0
8| 0 0 0 0 0 0 0 0 0 (5,1)->(5,2)->(5,3)->(5,4)
0 1 2 3 4 5 6 7 8
-----------------------------------------
0| 0 0 0 0 0 0 0 0 0
1| 0 0 0 0 0 0 0 0 0
2| 0 0 0 0 0 0 0 0 0
3| 0 0 0 1 0 0 0 0 0
4| 0 0 0 1 0 0 0 0 0
5| 0 X 0 1 X 0 0 0 0
6| 0 0 0 1 0 0 0 0 0
7| 0 0 0 0 0 0 0 0 0
8| 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8
-----------------------------------------
0| 0 0 0 0 0 0 0 0 0
1| 0 0 0 0 0 0 0 0 0
2| 0 0 0 0 0 0 0 0 0
3| 0 0 0 1 0 0 0 0 0
4| 0 0 0 1 0 0 0 0 0
5| 0 X 0 1 X 0 0 0 0
6| 0 0 X 1 X 0 0 0 0
7| 0 0 0 X 0 0 0 0 0
8| 0 0 0 0 0 0 0 0 0 (5,1)->(6,2)->(7,3)->(6,4)->(5,4)
0 1 2 3 4 5 6 7 8
-----------------------------------------
0| 0 0 0 1 0 0 0 0 0
1| 0 0 0 1 0 0 0 0 0
2| 0 0 0 1 0 0 0 0 0
3| 0 0 0 1 0 0 0 0 0
4| 0 0 0 1 0 0 0 0 0
5| 0 X 0 1 X 0 0 0 0
6| 0 0 0 1 0 0 0 0 0
7| 0 0 0 1 0 0 0 0 0
8| 0 0 0 1 0 0 0 0 0 无路可走
0 1 2 3 4 5 6 7 8
-----------------------------------------
0| 0 0 0 1 0 0 0 0 0
1| 0 0 0 1 0 0 0 0 0
2| 0 0 0 1 0 0 0 0 0
3| 0 0 0 1 0 0 0 0 0
4| 0 0 0 1 0 0 0 0 0
5| 0 X 0 1 X 0 0 0 0
6| 0 0 0 1 0 0 0 0 0
7| 0 0 0 1 0 0 0 0 0
8| 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8
-----------------------------------------
0| 0 0 0 1 0 0 0 0 0
1| 0 0 0 1 0 0 0 0 0
2| 0 0 0 1 0 0 0 0 0
3| 0 0 0 1 0 0 0 0 0
4| 0 0 0 1 0 0 0 0 0
5| 0 X 0 1 X 0 0 0 0
6| 0 X 0 1 X 0 0 0 0
7| 0 0 X 1 X 0 0 0 0
8| 0 0 0 X 0 0 0 0 0 (5,1)->(6,1)->(7,2)->(8,3)->(7,4)->(6,4)->(5,4)