递归路径查找0,1矩阵（并保存所有可能的路径）java

Question

我正在尝试编写一个递归方法，它可以找到一个路径，而不需要回溯到一个int矩阵中的一个位置，这个矩阵包含值0，1。0可以踩，1不行。我也限制了一条超过50步的路径。

Location是一个具有行和列值(x，y)的对象。locationEquals是一个函数，如果两个位置相同，则返回true，否则返回false。map变量是我试图在其中找到路径的矩阵。

private static List<List<Location>> options = new ArrayList<List<Location>>();
public static void PathFind(List<Location> path)
{
 Location current = path.get(path.size() - 1);
    boolean done = false;
    if(locationEquals(current,new Location(24,38)))
    {
        options.add(path);
        return;
    }
    if(path.size() > 50) done = true;
    if(!done)
    {
    try
    {
    if(map[current.row][current.col + 1] == 0)
    {
    if(!path.contains(new Location(current.row, current.col + 1)))
        {
            List<Location> temp = path;
            temp.add(new Location(current.row, current.col + 1));
            PathFind(temp);
        }
    }
    }
    catch (Exception e){}
            try
    {
    if(map[current.row - 1][current.col] == 0)
    {
        if(!path.contains(new Location(current.row - 1, current.col)))
        {
            List<Location> temp = path;
            temp.add(new Location(current.row - 1, current.col));
            PathFind(temp);
        }
    }
    }
    catch (Exception e){}
    try
    {
    if(map[current.row][current.col - 1] == 0)
    {
        if(!path.contains(new Location(current.row, current.col - 1)))
        {
            List<Location> temp = path;
            temp.add(new Location(current.row, current.col - 1));
            PathFind(temp);
        }
    }
    }
    catch (Exception e){}
    try
    {
    if(map[current.row + 1][current.col] == 0)
    {
        if(!path.contains(new Location(current.row + 1, current.col)))
        {
            List<Location> temp = path;
            temp.add(new Location(current.row + 1, current.col));
            PathFind(temp);
        }
    }
    }
    catch (Exception e){}
    }

执行以下代码后'选项'为空，这意味着它没有找到方法。但这个矩阵中肯定有方法，所以这是我代码中找不到的错误。

Answer 1

问题在于，每次进入递归的下一步时，您并没有创建一个新的列表(您的temp变量并不是真正的临时变量，因为它只是对您的路径的引用，而不是它的副本)。

为了解决这个问题，我替换了<代码>列表

所以代码是：

private static List<List<Location>> options = new ArrayList<List<Location>>();
public static void PathFind(List<Location> path) {
    Location current = path.get(path.size() - 1);
    boolean done = false;
    if (locationEquals(current, new Location(24, 38))) {
        options.add(path);
        return;
    }
    if (path.size() > 50) done = true;
    if (!done) {
        try {
            if (map[current.row][current.col + 1] == 0) {
                if (!path.contains(new Location(current.row, current.col + 1))) {
                    List<Location> temp = new ArrayList<>(path);
                    temp.add(new Location(current.row, current.col + 1));
                    PathFind(temp);
                }
            }
        } catch (Exception e) {
        }
        try {
            if (map[current.row - 1][current.col] == 0) {
                if (!path.contains(new Location(current.row - 1, current.col))) {
                    List<Location> temp = new ArrayList<>(path);
                    temp.add(new Location(current.row - 1, current.col));
                    PathFind(temp);
                }
            }
        } catch (Exception e) {
        }
        try {
            if (map[current.row][current.col - 1] == 0) {
                if (!path.contains(new Location(current.row, current.col - 1))) {
                    List<Location> temp = new ArrayList<>(path);
                    temp.add(new Location(current.row, current.col - 1));
                    PathFind(temp);
                }
            }
        } catch (Exception e) {
        }
        try {
            if (map[current.row + 1][current.col] == 0) {
                if (!path.contains(new Location(current.row + 1, current.col))) {
                    List<Location> temp = new ArrayList<>(path);
                    temp.add(new Location(current.row + 1, current.col));
                    PathFind(temp);
                }
            }
        } catch (Exception e) {
        }
    }
}