我需要用AI为一个项目编写一个蛇游戏。我在编写50x50二维阵列上实现的最短路径算法时遇到问题。我已经编写了AStar寻路算法的代码（参见下面的代码），但它似乎没有用。有人可以帮我纠正我的代码，也有人可以帮助我编写Dijktra算法，因为我正在努力为二维数组编码。值得一提的是，最短的路径算法是让我的蛇找到在2d板上到达苹果的最短路径。希望有人能提供帮助。 只是为了让我的问题更清楚：我的问题是我需要在二维数组上找到两点之间的最短路径，因为我是编码的初学者我需要帮助编写算法来找到初始点之间的最短路径和终点，如Dijktra或AStar。
//implementing a*
public int manhattenDistance(Point current, Point goal){
return Math.abs(current.getX()-goal.getX())+Math.abs(current.getY()-goal.getY());
}
public ArrayList<Point> aStar(Point myHead, Point apple){
ArrayList<Point> closedSer=new ArrayList<>();
ArrayList<Point> openSet=new ArrayList<>();
openSet.add(myHead);
ArrayList<Point> cameFrom=new ArrayList<>();
int[][] gscore=new int[50][50];
for(int i=0;i<gscore.length;i++){
for(int j=0;j<gscore.length;j++)
gscore[i][j]=Integer.MAX_VALUE;
}
gscore[myHead.getX()][myHead.getY()]=0;
int[][] fscore=new int[50][50];
for(int i=0;i<fscore.length;i++){
for(int j=0;j<fscore.length;j++)
fscore[i][j]=Integer.MAX_VALUE;
}
fscore[myHead.getX()][myHead.getY()]=manhattenDistance(myHead,apple);
while(!openSet.isEmpty()){
Point current; int[] fscores=new int[openSet.size()];
for (int i=0;i<openSet.size();i++){
Point p=openSet.get(i);
fscores[i]=manhattenDistance(p,apple);
}int min=fscores[0], index=openSet.size();
for(int i=0;i<fscores.length-1;i++){
if(fscores[i]<fscores[i+1]) {
min = fscores[i];
index = i;
}if(fscores[i+1]<min){
min=fscores[i+1]; index=i+1;
}
}
current=openSet.get(index-1);
if(current==apple) return cameFrom;//.toArray(new Point[cameFrom.size()]);// reconstructpath(cameFrom,current);
openSet.remove(index-1);
closedSer.add(current);
Point[] currentNeighbourstemp=current.getNeighbours();
ArrayList<Point> currentNeighbours=new ArrayList<>();
for(Point n:currentNeighbourstemp)
if(isOnBoard(n)) currentNeighbours.add(n);
/*for(int i=0;i<currentNeighbours.length;i++){
for(int j=0; j<openSet.size();j++)
if(currentNeighbours[i]==openSet.get(j)) continue;;
}*/
for (Point neighbour:currentNeighbours){
Double tentative_gscore=gscore[neighbour.getX()][neighbour.getY()]+distanceBetween(neighbour,current);
boolean in=false;
for(int i=0;i<openSet.size();i++){//checking if in oppenset
if(neighbour==openSet.get(i)) in=true;
}
if(!in) openSet.add(neighbour);
else if(tentative_gscore>=gscore[neighbour.getX()][neighbour.getY()]) continue;
gscore[neighbour.getX()][neighbour.getY()]=tentative_gscore.intValue();
fscore[neighbour.getX()][neighbour.getY()]=gscore[neighbour.getX()][neighbour.getY()]+manhattenDistance(neighbour,apple);
}
}
return cameFrom;//.toArray(new Point[cameFrom.size()]);
}
public Double distanceBetween(Point a,Point b){
return Math.sqrt((b.getX()-a.getX())*(b.getX()-a.getX())+(b.getY()-a.getY())*(b.getY()-a.getY()));
}
public static float invSqrt(float x) {
float xhalf=0.5f*x;
int i=Float.floatToIntBits(x);
i=0x5f3759df-(i>>1);
x=Float.intBitsToFloat(i);
x=x*(1.5f-xhalf*x*x);
return x;
}
public float gravityDistance(Point that,Point th){
if(this.equals(that)) return Float.MAX_VALUE;
return 20.0f*invSqrt(Math.abs(th.x-that.x)+Math.abs(th.y-that.y));
}
答案 0 :(得分：1)
这是Dijkstra最短路径算法的JAVA实现：
// A Java program for Dijkstra's single source shortest path algorithm.
// The program is for adjacency matrix representation of the graph.
class ShortestPath
{
/* A utility function to find the vertex with minimum distance value,
from the set of vertexes not yet included in shortest path tree */
static final int V = 9;
int minDistance(int dist[], boolean sptSet[])
{
// Initialize min value
int min = Integer.MAX_VALUE, min_index = -1;
for(int v = 0; v < V; v++)
{
if(sptSet[v] == false && dist[v] <= min)
{
min = dist[v];
min_index = v;
}
}
return min_index;
}
// A utility function to print the constructed distance array
void printSolution(int dist[], int n)
{
System.out.println("Vertex Distance from Source");
for(int i = 0; i < V; i++)
System.out.println(i+" \t\t "+dist[i]);
}
/* Function that implements Dijkstra's single source shortest path
algorithm for a graph represented using adjacency matrix
representation */
void dijkstra(int graph[][], int src)
{
int dist[] = new int[V]; /* The output array, dist[i] will hold
the shortest distance from src to i */
/* sptSet[i] will be true if vertex i is included in shortest
path tree or shortest distance from src to i is finalized */
Boolean sptSet[] = new Boolean[V];
for(int i = 0; i < V; i++)
{
dist[i] = Integer.MAX_VALUE;
sptSet[i] = false;
}
// Distance of source vertex from itself is always 0
dist[src] = 0;
//Find shortest path for all vertexes
for(int count = 0; count < V-1; count++)
{
/* Pick the minimum distance vertex from the set of vertexes
not yet processed. u is always equal to src in first
iteration. */
int u = minDistance(dist, sptSet);
// Mark the picked vertex as processed
sptSet[u] = true;
/* Update dist value of the adjacent vertexes of the
picked vertex. */
for(int v = 0; v < V; v++)
{
/* Update dist[v] only if it is not in sptSet, there is an
edge from u to v, and total weight of path from src to
v through u is smaller than current value of dist[v] */
if (!sptSet[v] && graph[u][v] && dist[u] != INT_MAX
&& dist[u]+graph[u][v] < dist[v])
dist[v] = dist[u] + graph[u][v];
}
}
// print the constructed distance array
printSolution(dist, V);
}
public static void main(String[] args)
{
// Create an example graph
int graph[][] = new int[][]{{0, 4, 0, 0, 0, 0, 0, 8, 0},
{4, 0, 8, 0, 0, 0, 0, 11, 0},
{0, 0, 7, 0, 9, 14, 0, 0, 0},
{0, 0, 0, 9, 0, 10, 0, 0, 0},
{0, 0, 0, 9, 0, 10, 0, 0, 0},
{0, 0, 4, 14, 10, 0, 2, 0, 0},
{0, 0, 0, 0, 0, 2, 0, 1, 6},
{8, 11, 0, 0, 0, 0, 1, 0, 7},
{0, 0, 2, 0, 0, 0, 6, 7, 0}};
ShortestPath t = new ShortestPath();
t.dijkstra(graph, 0);
}
}
代码非常自我解释。需要注意的一些要点：
希望这有帮助！如果您在理解算法时遇到任何问题，请告诉我。祝你好运！